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Tag: caloric restriction

  • Lose Weight with Cumin and Saffron?  | NutritionFacts.org

    The spice cumin can work as well as orlistat, the “anal leakage” obesity drug.

    In my video Friday Favorites: Benefits of Black Cumin for Weight Loss, I discussed how a total of 17 randomized controlled trials showed that the simple spice could reduce cholesterol and triglyceride levels. And its side effects? A weight-loss effect.

    Saffron is another spice found to be effective for treating a major cause of suffering—depression, in this study, with a side effect of decreased appetite. Indeed, when put to the test in a randomized, double-blind, placebo-controlled trial, saffron was found to lead to significant weight loss, five pounds more than placebo, and an extra inch off the waist in eight weeks. The dose of saffron used in the study was the equivalent of drinking a cup of tea made from a large pinch of saffron threads.

    Suspecting the active ingredient might be crocin, the pigment in saffron that accounts for its crimson color, as shown here and at 0:59 in my video Friday Favorites: Benefits of Cumin and Saffron for Weight Loss, researchers also tried giving people just the purified pigment.

    That also led to weight loss, but it didn’t do as well as the full saffron extract and only beat the placebo by two pounds and half an inch off the waist. The mechanism appeared to be appetite suppression, as the crocin group ended up averaging about 80 fewer calories a day, whereas the full saffron group consumed an average of 170 fewer daily calories, as you can see below and at 1:21 in my video.

    A similar study looked specifically at snacking frequency. The researchers thought that the mood-boosting effects of saffron might cut down on stress-related eating. Indeed, eight weeks of a saffron extract halved snack intake, compared to a placebo. There was also a slight but statistically significant weight loss of about two pounds, as you can see here and at 1:41 in my video, which is pretty remarkable, given that tiny doses were utilized—about 100 milligrams, which is equivalent to about an eighth of a teaspoon of the spice.

    The problem is that saffron is the most expensive spice in the world. It’s composed of delicate threads sticking out of the saffron crocus flower. Each flower produces only a few threads, so about 50,000 flowers are needed to make a single pound of spice. That’s enough flowers to cover a football field. So, that pinch of saffron could cost a dollar a day.

    That’s why, in my 21 Tweaks to accelerate weight loss in How Not to Diet, I include black cumin, instead of saffron, as you can see here and at 2:30 in my video. And, at a quarter teaspoon a day, the daily dose of black cumin would only cost three cents.

    What about just regular cumin? Used in cuisines around the world from Tex-Mex to South Asian, cumin is the second most popular spice on Earth after black pepper. It is one of the oldest cultivated plants with a range of purported medicinal uses, but only recently has it been put to the test for weight loss. Those randomized to a half teaspoon at both lunch and dinner over three months lost about four more pounds and an extra inch off their waist. The spice was found to be comparable to the obesity drug known as orlistat.

    If you remember, orlistat is the “anal leakage” drug sold under the brand names Alli and Xenical. The drug company apparently prefers the term “faecal spotting” to describe the rectal discharge it causes, though. The drug company’s website offered some helpful tips, including: “It’s probably a smart idea to wear dark pants, and bring a change of clothes with you to work.” You know, just in case their drug causes you to poop in your pants at the office.

    I think I’ll stick with the cumin, thank you very much.

    Doctor’s Note

    The video on black cumin that I mentioned is Friday Favorites: Benefits of Black Cumin Seed (Nigella Sativa) for Weight Loss.

    My other videos on saffron are in the related posts below.

    For an in-depth dive into weight loss, see my book How Not to Diet. 

    Michael Greger M.D. FACLM

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  • Taking Advantage of Sensory-Specific Satiety  | NutritionFacts.org

    How can we use sensory-specific satiety to our advantage?

    When we eat the same foods over and over, we become habituated to them and end up liking them less. That’s why the “10th bite of chocolate, for example, is desired less than the first bite.” We have a built-in biological drive to keep changing up our foods so we’ll be more likely to hit all our nutritional requirements. The drive is so powerful that even “imagined consumption reduces actual consumption.” When study participants imagined again and again that they were eating cheese and were then given actual cheese, they ate less of it than those who repeatedly imagined eating that food fewer times, imagined eating a different food (such as candy), or did not imagine eating the food at all.

    Ironically, habituation may be one of the reasons fad “mono diets,” like the cabbage soup diet, the oatmeal diet, or meal replacement shakes, can actually result in better adherence and lower hunger ratings compared to less restrictive diets.

    In the landmark study “A Satiety Index of Common Foods,” in which dozens of foods were put to the test, boiled potatoes were found to be the most satiating food. Two hundred and forty calories of boiled potatoes were found to be more satisfying in terms of quelling hunger than the same number of calories of any other food tested. In fact, no other food even came close, as you can see below and at 1:14 in my video Exploiting Sensory-Specific Satiety for Weight Loss.

    No doubt the low calorie density of potatoes plays a role. In order to consume 240 calories, nearly one pound of potatoes must be eaten, compared to just a few cookies, and even more apples, grapes, and oranges must be consumed. Each fruit was about 40 percent less satiating than potatoes, though, as shown here and at 1:45 in my video. So, an all-potato diet would probably take the gold—the Yukon gold—for the most bland, monotonous, and satiating diet.

    A mono diet, where only one food is eaten, is the poster child for unsustainability—and thank goodness for that. Over time, they can lead to serious nutrient deficiencies, such as blindness from vitamin A deficiency in the case of white potatoes.

    The satiating power of potatoes can still be brought to bear, though. Boiled potatoes beat out rice and pasta in terms of a satiating side dish, cutting as many as about 200 calories of intake off a meal. Compared to boiled and mashed potatoes, fried french fries or even baked fries do not appear to have the same satiating impact.

    To exploit habituation for weight loss while maintaining nutrient abundance, we could limit the variety of unhealthy foods we eat while expanding the variety of healthy foods. In that way, we can simultaneously take advantage of the appetite-suppressing effects of monotony while diversifying our fruit and vegetable portfolio. Studies have shown that a greater variety of calorie-dense foods, like sweets and snacks, is associated with excess body fat, but a greater variety of vegetables appears protective. When presented with a greater variety of fruit, offered a greater variety of vegetables, or given a greater variety of vegetable seasonings, people may consume a greater quantity, crowding out less healthy options.

    The first 20 years of the official Dietary Guidelines for Americans recommended generally eating “a variety of foods.” In the new millennium, they started getting more precise, specifying a diversity of healthier foods, as seen below and at 3:30 in my video. 

    A pair of Harvard and New York University dietitians concluded in their paper “Dietary Variety: An Overlooked Strategy for Obesity and Chronic Disease Control”: “Choose and prepare a greater variety of plant-based foods,” recognizing that a greater variety of less healthy options could be counterproductive.

    So, how can we respond to industry attempts to lure us into temptation by turning our natural biological drives against us? Should we never eat really delicious food? No, but it may help to recognize the effects hyperpalatable foods can have on hijacking our appetites and undermining our body’s better judgment. We can also use some of those same primitive impulses to our advantage by minimizing our choices of the bad and diversifying our choices of the good. In How Not to Diet, I call this “Meatball Monotony and Veggie Variety.” Try picking out a new fruit or vegetable every time you shop.

    In my own family’s home, we always have a wide array of healthy snacks on hand to entice the finickiest of tastes. The contrasting collage of colors and shapes in fruit baskets and vegetable platters beat out boring bowls of a single fruit because they make you want to mix it up and try a little of each. And with different healthy dipping sauces, the possibilities are endless.

    Michael Greger M.D. FACLM

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  • Dietary Diversity and Overeating  | NutritionFacts.org

    Big Food uses our hard-wired drive for dietary diversity against us.

    How did we evolve to solve the daunting task of selecting a diet that supplies all the essential nutrients? Dietary diversity. By eating a variety of foods, we increase our chances of hitting all the bases. If we only ate for pleasure, we might just stick with our favorite food to the exclusion of all others, but we have an innate tendency to switch things up.

    Researchers found that study participants ended up eating more calories when provided with three different yogurt flavors than just one, even if that one is the chosen favorite. So, variation can trump sensation. They don’t call it the spice of life for nothing.

    It appears to be something we’re born with. Studies on newly weaned infants dating back nearly a century show that babies naturally choose a variety of foods even over their preferred food. This tendency seems to be driven by a phenomenon known as sensory-specific satiety.

    Researchers found that, “within 2 minutes after eating the test meal, the pleasantness of the taste, smell, texture, and appearance of the eaten food decreased significantly more than for the uneaten foods.” Think about how the first bite of chocolate tastes better than the last bite. Our body tires of the same sensations and seeks out novelty by rekindling our appetite every time we’re presented with new foods. This helps explain the “dessert effect,” where we can be stuffed to the gills but gain a second wind when dessert arrives. What was adaptive for our ancient ancestors to maintain nutritional adequacy may be maladaptive in the age of obesity.

    When study participants ate a “varied four-course meal,” they consumed 60 percent more calories than those given the same food for each course. It’s not only that we get bored; our body has a different physiological reaction.

    As you can see below and at 2:13 in my video How Variation Can Trump Sensation and Lead to Overeating, researchers gave people a squirt of lemon juice, and their salivary glands responded with a squirt of saliva. But when they were given lemon juice ten times in a row, they salivated less and less each time. When they got the same amount of lime juice, though, their salivation jumped right back up. We’re hard-wired to respond differently to new foods. 
    Whether foods are on the same plate, are at the same meal, or are even eaten on subsequent days, the greater the variety, the more we tend to eat. When kids had the same mac and cheese dinner five days in a row, they ended up eating hundreds fewer calories by the fifth day, compared to kids who got a variety of different meals, as you can see below and at 2:35 in my video.

    Even just switching the shape of food can lead to overeating. When kids had a second bowl of mac and cheese, they ate significantly more when the noodles were changed from elbow macaroni to spirals. People allegedly eat up to 77 percent more M&Ms if they’re presented with ten different colors instead of seven, even though all the colors taste the same. “Thus, it is clear that the greater the differences between foods, the greater the enhancement of intake,” the greater the effect. Alternating between sweet and savory foods can have a particularly appetite-stimulating effect. Do you see how, in this way, adding a diet soda, for instance, to a fast-food meal can lead to overconsumption?

    The staggering array of modern food choices may be one of the factors conspiring to undermine our appetite control. There are now tens of thousands of different foods being sold.

    The so-called supermarket diet is one of the most successful ways to make rats fat. Researchers tried high-calorie food pellets, but the rats just ate less to compensate. So, they “therefore used a more extreme diet…[and] fed rats an assortment of palatable foods purchased at a nearby supermarket,” including such fare as cookies, candy, bacon, and cheese, and the animals ballooned. The human equivalent to maximize experimental weight gain has been dubbed the cafeteria diet.

    It’s kind of the opposite of the original food dispensing device I’ve talked about before. Instead of all-you-can-eat bland liquid, researchers offered free all-you-can-eat access to elaborate vending machines stocked with 40 trays with a dizzying array of foods, like pastries and French fries. Participants found it impossible to maintain energy balance, consistently consuming more than 120 percent of their calorie requirements.

    Our understanding of sensory-specific satiety can be used to help people gain weight, but how can we use it to our advantage? For example, would limiting the variety of unhealthy snacks help people lose weight? Two randomized controlled trials made the attempt and failed to show significantly more weight loss in the reduced variety diet, but they also failed to get people to make much of a dent in their diets. Just cutting down on one or two snack types seems insufficient to make much of a difference, as seen below and at 4:44 in my video. A more drastic change may be needed, which we’ll cover next.

    Michael Greger M.D. FACLM

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  • Hijacking Our Appetites  | NutritionFacts.org

    I debunk the myth of protein as the most satiating macronutrient.

    The importance of satiety is underscored by a rare genetic condition known as Prader-Willi syndrome. Children with the disorder are born with impaired signaling between their digestive system and their brain, so they don’t know when they’re full. “Because no sensation of satiety tells them to stop eating or alerts their body to throw up, they can accidentally consume enough in a single binge to fatally rupture their stomach.” Without satiety, food can be “a death sentence.”

    Protein is often described as the most satiating macronutrient. People tend to report feeling fuller after eating a protein-rich meal, compared to a carbohydrate- or fat-rich one. The question is: Does that feeling of fullness last? From a weight-loss standpoint, satiety ratings only matter if they end up cutting down on subsequent calorie intake, and even a review funded by the meat, dairy, and egg industries acknowledges that this does not seem to be the case for protein. Hours later, protein consumed earlier doesn’t tend to end up cutting calories later on.

    Fiber-rich foods, on the other hand, can suppress appetite and reduce subsequent meal intake more than ten hours after consumption—even the next day—because their site of action is 20 feet down in the lower intestine. Remember the ileal brake from my Evidence-Based Weight Loss lecture? When researchers secretly infused nutrients into the end of the small intestine, study participants spontaneously ate as many as hundreds fewer calories at a meal. Our brain gets the signal that we are full, from head to tail.

    We were built for gluttony. “It is a wonderful instinct, developed over millions of years, for times of scarcity.” Stumbling across a rare bounty, those who could fill themselves the most to build up the greatest reserves would be more likely to pass along their genes. So, we are hard-wired not just to eat until our stomach is full, but until our entire digestive tract is occupied. Only when our brain senses food all the way down at the end does our appetite fully dial down.

    Fiber-depleted foods get rapidly absorbed early on, though, so much of it never makes it down to the lower gut. As such, if our diet is low in fiber, no wonder we’re constantly hungry and overeating; our brain keeps waiting for the food that never arrives. That’s why people who even undergo stomach-stapling surgeries that leave them with a tiny two-tablespoon-sized stomach pouch can still eat enough to regain most of the weight they initially lost. Without sufficient fiber, transporting nutrients down our digestive tract, we may never be fully satiated. But, as I described in my last video, one of the most successful experimental weight-loss interventions ever reported in the medical literature involved no fiber at all, as you can see here and at 2:47 in my video Foods Designed to Hijack Our Appetites.

    At first glance, it might seem obvious that removing the pleasurable aspects of eating would cause people to eat less, but remember, that’s not what happened. The lean participants continued to eat the same amount, taking in thousands of calories a day of the bland goop. Only those who were obese went from eating thousands of calories a day down to hundreds, as shown below and at 3:22 in my video. And, again, this happened inadvertently without them apparently even feeling a difference. Only after eating was disconnected from the reward was the body able to start rapidly reining in the weight.

    We appear to have two separate appetite control systems: “the homeostatic and hedonic pathways.” The homeostatic pathway maintains our calorie balance by making us hungry when energy reserves are low and abolishes our appetite when energy reserves are high. “In contrast, hedonic or reward-based regulation can override the homeostatic pathway” in the face of highly palatable foods. This makes total sense from an evolutionary standpoint. In the rare situations in our ancestral history when we’d stumble across some calorie-dense food, like a cache of unguarded honey, it would make sense for our hedonic drive to jump into the driver’s seat to consume the scarce commodity. Even if we didn’t need the extra calories at the time, our body wouldn’t want us to pass up that rare opportunity. Such opportunities aren’t so rare anymore, though. With sugary, fatty foods around every corner, our hedonic drive may end up in perpetual control, overwhelming the intuitive wisdom of our bodies.

    So, what’s the answer? Never eat really tasty food? No, but it may help to recognize the effects hyperpalatable foods can have on hijacking our appetites and undermining our body’s better judgment.

    Ironically, some researchers have suggested a counterbalancing evolutionary strategy for combating the lure of artificially concentrated calories. Just as pleasure can overrule our appetite regulation, so can pain. “Conditioned food aversions” are when we avoid foods that made us sick in the past. That may just seem like common sense, but it is actually a deep-seated evolutionary drive that can defy rationality. Even if we know for a fact a particular food was not the cause of an episode of nausea and vomiting, our body can inextricably tie the two together. This happens, for example, with cancer patients undergoing chemotherapy. Consoling themselves with a favorite treat before treatment can lead to an aversion to their favorite food if their body tries to connect the dots. That’s why oncologists may advise the “scapegoat strategy” of only eating foods before treatment that you are okay with, never wanting to eat again.

    Researchers have experimented with inducing food aversions by having people taste something before spinning them in a rotating chair to cause motion sickness. Eureka! A group of psychologists suggested: “A possible strategy for encouraging people to eat less unhealthy food is to make them sick of the food, by making them sick from the food.” What about using disgust to promote eating more healthfully? Children as young as two-and-a-half years old will throw out a piece of previously preferred candy scooped out of the bottom of a clean toilet.

    Thankfully, there’s a way to exploit our instinctual drives without resorting to revulsion, aversion, or bland food, which we’ll explore next.

    Michael Greger M.D. FACLM

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  • Lose 200 Lbs Without Feeling Hungry  | NutritionFacts.org

    I dive into one of the most fascinating series of studies I’ve ever come across.

    Anyone can lose weight by eating less food. Anyone can be starved thin. Starvation diets are rarely sustainable, though, since hunger pangs drive us to eat. We feel unsatisfied and unsatiated on low-calorie diets. We do have some level of voluntary control, of course, but our deep-seated instinctual drives may win out in the end.

    For example, we can consciously hold our breath. Try it right now. How long can you go before your body’s self-preservation mechanisms take over and overwhelm your deliberate intent not to breathe? Our body has our best interests at heart and is too smart to allow us to suffocate ourselves—or starve ourselves, for that matter. If our body were really that smart, though, how could it let us become obese? Why doesn’t our body realize when we’re too heavy and allow us the leeway to slim down? Maybe our body is very aware and actively trying to help, but we’re somehow undermining those efforts. How could we test this theory to see if that’s true?

    So many variables go into choosing what we eat and how much. “The eating process involves an intricate mixture of physiologic, psychologic, cultural, and esthetic considerations.” To strip all that away and stick just to the physiologic variable, Columbia University researchers designed a series of famous experiments using a “food dispensing device.” The term “food” is used very loosely here. As you can see at 2:02 in my video 200-Pound Weight Loss Without Hunger, the researchers’ feeding machine was a tube hooked up to a pump that delivered a mouthful of bland liquid formula every time a button was pushed. Research participants were instructed to eat as much or as little as they wanted at any time. In this way, eating was reduced to just the rudimentary hunger drive. Without the usual trappings of “sociability,” meal ceremony, and the pleasures of the palate, how much would people be driven to eat? 
    Put a normal-weight person in this scenario, and something remarkable happens. Day after day, week after week, with nothing more than their hunger to guide them, they eat exactly as much as they need, perfectly maintaining their weight, as shown below and at 2:36 in my video.

    They needed about 3,000 calories a day, and that’s just how much they unknowingly gave themselves. Their body just intuitively seemed to know how many times to press that button, as seen here and at 2:48 in my video.

    Put a person with obesity in that same scenario, and something even more remarkable happens. Driven by hunger alone, with the enjoyment of eating stripped away, they wildly undershoot, giving themselves a mere 275 calories a day, total. They could eat as much as they wanted, but they just weren’t hungry. It’s as if their body knew how massively overweight they were, so it dialed down their natural hunger drive to almost nothing. One participant started the study at 400 pounds and steadily lost weight. After 252 days of sipping the bland liquid, he lost 200 pounds, as you can see here and at 3:35 in my video.

    This groundbreaking discovery was initially interpreted to mean that obesity is not caused by some sort of metabolic disturbance that drives people to overeat. In fact, the study suggested quite the opposite. Instead, overeating appeared to be a function of the meaning people attached to food, “aside from its use as fuel,” whether as a source of pleasure or perhaps as relief from boredom or stress. In this way, obesity seemed more psychological than physical. Subsequent experiments with the feeding machine, though, flipped such conceptions on their head once again.

    When researchers covertly doubled the calorie concentration of the formula given to lean study participants, they unconsciously cut their consumption in half to continue to perfectly maintain their weight, as seen here and at 4:24 in my video. Their body somehow detected the change in calorie load and sent signals to the brain to press the button half as often to compensate. Amazing!

    When the same was done with people with obesity, though, nothing changed. They continued to drastically undereat just as much as before. Their body seems incapable of detecting or reacting to the change in calorie load, suggesting a physiological inability to regulate intake, as shown below and at 4:40 in my video. 
    Might the brains of persons with obesity somehow be insensitive to internal satiety signals? We don’t know if it’s cause or effect. Maybe that’s why they’re obese in the first place, or maybe the body knows how obese it is and shuts down its hunger drive regardless of the calorie concentration. Indeed, the participants with obesity continued to steadily lose weight eating out of the machine, regardless of the calorie concentration and the food being dispensed, as you can see here and at 5:19 in my video. 
    It would be interesting to see if they regained the ability to respond to changing calorie intake once they reached their ideal weight. Regardless, what can we apply from these remarkable studies to facilitate weight loss out in the real world? We’ll explore just that question next.

    Michael Greger M.D. FACLM

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  • Boosting BDNF Levels in Our Brain to Treat Depression  | NutritionFacts.org

    We can raise BDNF levels in our brain by fasting and exercising, as well as by eating and avoiding certain foods.

    There is accumulating evidence that brain-derived neurotrophic factor (BDNF) may be playing a role in human depression. BDNF controls the growth of new nerve cells. “So, low levels of this peptide could lead to an atrophy of specific brain areas such as the amygdala and the hippocampus, as it has been observed among depressed patients.” That may be one of the reasons that exercise is so good for our brains. Start an hour-a-day exercise regimen, and, within three months, there can be a quadrupling of BDNF release from our brain, as seen below and at 0:35 in my video How to Boost Brain BDNF Levels for Depression Treatment.

    This makes sense. Any time we were desperate to catch prey (or desperate not to become prey ourselves), we needed to be cognitively sharp. So, when we’re fasting, exercising, or in a negative calorie balance, our brain starts churning out BDNF to make sure we’re firing on all cylinders. Of course, Big Pharma is eager to create drugs to mimic this effect, but is there any way to boost BDNF naturally? Yes, I just said it: fasting and exercising. Is there anything we can add to our diet to boost BDNF?

    Higher intakes of dietary flavonoids appear to be protectively associated with symptoms of depression. The Harvard Nurses’ Health Study followed tens of thousands of women for years and found that those who were consuming the most flavonoids appeared to reduce their risk of becoming depressed. Flavonoids occur naturally in plants, so there’s a substantial amount in a variety of healthy foods. But how do we know the benefits are from the flavonoids and not just from eating more healthfully in general? We put it to the test.

    Some fruits and vegetables have more flavonoids than others. As shown below and at 1:51 in my video, apples have more than apricots, plums more than peaches, red cabbage more than white, and kale more than cucumbers. Researchers randomized people into one of three groups: more high-flavonoid fruits and vegetables, more low-flavonoid fruits and vegetables, or no extra fruits and vegetables at all. After 18 weeks, only the high-flavonoid group got a significant boost in BDNF levels, which corresponded with an improvement in cognitive performance. The BDNF boost may help explain why each additional daily serving of fruits or vegetables is associated with a 3 percent decrease in the risk of depression. 

    What’s more, as seen here and at 2:27 in my video, a teaspoon a day of the spice turmeric may boost BNDF levels by more than 50 percent within a month. This is consistent with the other randomized controlled trials that have so far been done. 

    Nuts may help, too. In the PREDIMED study, where people were randomized to receive weekly batches of nuts or extra-virgin olive oil, the nut group lowered their risk of having low BDNF levels by 78 percent, as shown below and at 2:46.

    And BDNF is not implicated only in depression, but schizophrenia. When individuals with schizophrenia underwent a 12-week exercise program, they got a significant boost in their BDNF levels, which led the researchers to “suggest that exercise-induced modulation of BDNF may play an important role in developing non-pharmacological treatment for chronic schizophrenic patients.”

    What about schizophrenia symptoms? Thirty individuals with schizophrenia were randomized to ramp up to 40 minutes of aerobic exercise three times a week or not, and there did appear to be an improvement in psychiatric symptoms, such as hallucinations, as well as an increase in their quality of life, with exercise. In fact, researchers could actually visualize what happened in their brains. Loss of brain volume in a certain region appears to be a feature of schizophrenia, but 30 minutes of exercise, three times a week, resulted in an increase of up to 20 percent in the size of that region within three months, as seen here and at 3:46 in my video. 

    Caloric restriction may also increase BDNF levels in people with schizophrenia. So, researchers didn’t just have study participants eat less, but more healthfully, too—less saturated fat and sugar, and more fruits and veggies. The study was like the Soviet fasting trials for schizophrenia that reported truly unbelievable results, supposedly restoring people to function, and described fasting as “an unparalleled achievement in the treatment of schizophrenia”—but part of the problem is that the diagnostic system the Soviets used is completely different than ours, making any results hard to interpret. There was a subgroup that seemed to correspond to the Western definition, but they still reported 40 to 60 percent improvement rates from fasting, but fasting wasn’t all they did. After the participants fasted for up to a month, they were put on a meat- and egg-free diet. So, when the researchers reported these remarkable effects even years later, they were for those individuals who stuck with the meat- and egg-free diet. Evidently, the closer the diet was followed, the better the effect, and those who broke the diet relapsed. The researchers noted: “Not all patients can remain vegetarian, but they must not take meat for at least six months, and then in very small portions.” We know from randomized controlled trials that simply eschewing meat and eggs can improve mental states within just two weeks, so it’s hard to know what role fasting itself played in the reported improvements.

    A single high-fat meal can drop BDNF levels within hours of consumption, and we can prove it’s the fat itself by seeing the same result after injecting fat straight into our veins. Perhaps that helps explain why increased consumption of saturated fats in a high-fat diet may contribute to brain dysfunction—that is, neurodegenerative diseases, long-term memory loss, and cognitive impairment. It may also help explain why the standard American diet has been linked to a higher risk of depression, as dietary factors modulate the levels of brain-derived neurotrophic factor.

    Michael Greger M.D. FACLM

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  • The Pros of Early Time-Restricted Eating  | NutritionFacts.org

    The Pros of Early Time-Restricted Eating  | NutritionFacts.org

    Calories eaten in the morning count less than calories eaten in the evening, and they’re healthier, too.
     
    Time-restricted feeding, where you limit the same amount of eating to a narrow evening window, has benefits compared to eating in the evening and earlier in the day, but it also has adverse effects because you’re eating so much, so late, as you can see below and at 0:12 my video The Benefits of Early Time-Restricted Eating. 

    The best of both worlds was demonstrated in 2018 when researchers put time-restricted feeding into a narrow window earlier in the day. As you can see below and at 0:28 in my video, individuals who were randomized to eat the same food, but only during an 8:00 a.m. to 3:00 p.m. eating window, experienced a drop in blood pressure, oxidative stress, and insulin resistance, even when all of the study subjects were maintained at the same weight. Same food, same weight, but with different results. The drops in blood pressure were extraordinary, from 123/82 down to 112/72 in five weeks, and that is comparable to the effectiveness of potent blood-pressure drugs.


    The longest study to date on time-restricted feeding only lasted for 16 weeks. It was a pilot study without a control group that involved only eight people, but the results are still worth noting. Overweight individuals, who, like most of us, had been eating for more than 14 hours a day, were instructed to stick to a consistent 10- to 12-hour feeding window of their own choosing, as you can see below and at 1:17 in my video. On average, they were able to successfully reduce their daily eating duration by about four and a half hours and had lost seven pounds within 16 weeks. 

    They also reported feeling more energetic and sleeping better, as seen in the graph below and at 1:32 in my video. This may help explain why “all participants voluntarily expressed an interest in continuing unsupervised with the 10-11 hr time-restricted eating regimen after the conclusion of the 16-week supervised intervention.” You don’t often see that after weight-loss studies. 

    Even more remarkably, eight months later and even one year post-study, they had retained their improved energy and sleep (see in the graph below and 1:55 in my video), as well as retained their weight loss (see in the graph below and 1:58 in my video)—all from one of the simplest of interventions: sticking to a consistent 10- to 12-hour feeding window of their own choosing. 
    How did it work? Even though the study “participants were not overtly asked to change nutrition quality or quantity,” they appeared to unintentionally eat hundreds of fewer calories a day. With self-selected time frames for eating, you wouldn’t necessarily think to expect circadian benefits, but because they had been asked to keep the eating window consistent throughout the week, “metabolic jet lag could be minimized.” The thinking is that because people tend to start their days later on weekends, they disrupt their own circadian rhythm. And, indeed, it is as if they had flown a few time zones west on Friday evening, then flew back east on Monday morning, as you can see in the graph below and at 2:40 in my video. So, some of the metabolic advantages may have been due to maintaining a more regular eating schedule. 


    Early or mid-day time-restricted feeding may have other benefits as well. Prolonged nightly fasting with reduced evening food intake has been associated with lower levels of inflammation and has also been linked to better blood sugar control, both of which might be expected to lower the risk of diseases, such as breast cancer. So, data were collected on thousands of breast cancer survivors to see if nightly fasting duration made a difference. Those who couldn’t go more than 13 hours every night without eating had a 36 percent higher risk of cancer recurrence. These findings have led to the suggestion that efforts to “avoid eating after 8 pm and fast for 13 h or more overnight may be a beneficial consideration for those patients looking to decrease cancer risk and recurrence,” though we would need a randomized controlled trial to know for sure. 
     
    Early time-restricted feeding may even play a role in the health of perhaps the longest-living population in the world, the Seventh-day Adventist Blue Zone in California. As you can see in the graph below and at 3:55 in my video, slim, vegetarian, nut-eating, exercising, non-smoking Adventists live about a decade longer than the general population. 

    Their greater life expectancy has been ascribed to these healthy lifestyle behaviors, but there’s one lesser-known component that may also be playing a role. Historically, eating two large meals a day, breakfast and lunch, with a prolonged overnight fast, was a part of Adventist teachings. Today, only about one in ten Adventists surveyed were eating just two meals a day. However, most of them, more than 60 percent of them, reported that breakfast or lunch was their largest meal of the day, as you can see below and at 4:26 in my video. Though this has yet to be studied concerning longevity, frontloading one’s calories earlier in the day with a prolonged nightly fast has been associated with significant weight loss over time. This led the researchers to conclude: “Eating breakfast and lunch 5–6 h apart and making the overnight fast last 18–19 h may be a useful practical strategy” for weight control. The weight may be worth the wait. 


    For more on fasting, click here. 
     
    My big takeaway from all of the intermittent fasting research I looked at is, whenever possible, eat earlier in the day. At the very least, avoid late-night eating whenever you can. Eating breakfast like a king and lunch like a prince, with or without an early dinner for a pauper, would probably be best. 
     
    For more on fasting, fasting for disease reversal, and fasting and cancer, check the related videos below.  

    Michael Greger M.D. FACLM

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  • What the Science Says About Time-Restricted Eating  | NutritionFacts.org

    What the Science Says About Time-Restricted Eating  | NutritionFacts.org

    Are there benefits to giving yourself a bigger daily break from eating? 
     
    The reason many blood tests are taken after an overnight fast is that meals can tip our system out of balance, bumping up certain biomarkers for disease, such as blood sugars, insulin, cholesterol, and triglycerides. Yet, as you can see in the graph below and at 0:20 in my video Time-Restricted Eating Put to the Test, fewer than one in ten Americans may even make it 12 hours without eating. As evolutionarily unnatural as getting three meals a day is, most of us are eating even more than that. One study used a smartphone app to record more than 25,000 eating events and found that people tended to eat about every three hours over an average span of about 15 hours a day. Might it be beneficial to give our bodies a bigger break? 

    Time-restricted feeding is “defined as fasting for periods of at least 12 hours but less than 24 hours,” and this involves trying to confine caloric intake to a set window of time, typically ranging from 3 to 4 hours, 7 to 9 hours, or 10 to 12 hours a day, which results in a daily fast lasting 12 to 21 hours. When mice are restricted to a daily feeding window, they gain less weight even when fed the same amount as mice “with ad-lib access.” Rodents have such high metabolisms, though, that a single day of fasting can starve away as much as 15 percent of their lean body mass. This makes it difficult to extrapolate from mouse models. You don’t know what happens in humans until you put it to the test. 
     
    The drop-out rates in time-restricted feeding trials certainly appear lower than most prolonged forms of intermittent fasting, suggesting it’s more easily tolerable, but does it work? Researchers found that when people stopped eating from 7:00 p.m. to 6:00 a.m. for two weeks, they lost about a pound each week compared to no time restriction. Note that “there were no additional instructions or recommendations on the amount or type of food consumed,” and no gadgets, calorie counting, or record-keeping either. The study participants were just told to limit their food intake to the hours of 6:00 a.m. and 7:00 p.m., a simple intervention that’s easy to understand and put into practice. 
     
    The next logical step? Put it to the test for months instead of just weeks. Obese men and women were asked to restrict eating to the eight-hour window between 10:00 a.m. and 6:00 p.m. Twelve weeks later, they had lost nearly seven pounds, as you can see in the graph below and at 2:18 in my video. This deceptively simple intervention may be operating from several different angles. People not only tend to eat more food later in the day, but eat higher fat foods later in the day. By eliminating eating in the late-evening hours, one removes prime-time snacking on the couch, a high-risk time for overeating. And, indeed, during the no-eating-after-7:00-p.m. study, the subjects were inadvertently eating about 250 fewer calories a day. Then, there are also the chronobiological benefits of avoiding late-night eating. 

    I did a whole series of videos about the role our circadian rhythms have in the obesity epidemic, how the timing of meals can be critical, and how we can match meal timing to our body clocks. Just to give you a taste: Did you know that calories eaten at dinner are significantly more fattening than the same number of calories eaten at breakfast? See the table below and at 3:08 in my video. 

    Calories consumed in the morning cause less weight gain than the same calories eaten in the evening. A diet with a bigger breakfast causes more weight loss than the same exact diet with a bigger dinner, as you can see in the graph below and at 3:21 in my video, and nighttime snacks are more fattening than the same snacks if eaten in the daytime. Thanks to our circadian rhythms, metabolic slowing, hunger, carbohydrate intolerance, triglycerides, and a propensity for weight gain are all things that go bump in the night.  


    What about the fasting component of time-restricted feeding? There’s already the double benefit of getting fewer calories and avoiding night-time eating. Does the fact that you’re fasting for 11 or 16 hours a day play any role, considering the average person may only make it about 9 hours a day without eating? How would you design an experiment to test that? What if you randomized people into two groups and had both groups eat the same number of calories a day and also eat late into the evening, but one group fasted even longer, for 20 hours? That’s exactly what researchers at the USDA and National Institute of Aging did. 
     
    Men and women were randomized to eat three meals a day or fit all of those same calories into a four-hour window between 5:00 p.m. and 9:00 p.m., then fast the rest of the day. If the weight-loss benefits from the other two time-restricted feeding studies were due to the passive calorie restriction or avoidance of late-night eating, then, presumably, both of these groups should end up the same because they’re both eating the same amount and they’re both eating late. That’s not what happened, though. As you can see below and at 4:49 in my video, after eight weeks, the time-restricted feeding group ended up with less body fat, nearly five pounds less. They got about the same number of calories, but they lost more weight. 

    As seen below and at 5:00 in my video, a similar study with an eight-hour eating window resulted in three more pounds of fat loss. So, there does seem to be something to giving your body daily breaks from eating around the clock.


    Because that four-hour eating window in the study was at night, though, the participants suffered the chronobiological consequences—significant elevations in blood pressure and cholesterol levels—despite the weight loss, as you can see below and at 5:13 in my video. The best of both worlds was demonstrated in 2018: early time-restricted feeding, eating with a narrow window earlier in the day, which I covered in my video The Benefits of Early Time-Restricted Eating. 


    Isn’t that mind-blowing about the circadian rhythm business? Calories in the morning count less and are healthier than calories in the evening. So, if you’re going to skip a meal to widen your daily fasting window, skip dinner instead of breakfast. 

    If you missed any of the other videos in this fasting series, check out the related videos below. 

    Michael Greger M.D. FACLM

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  • A Look at the 5:2 Diet and the Fasting-Mimicking Diet  | NutritionFacts.org

    A Look at the 5:2 Diet and the Fasting-Mimicking Diet  | NutritionFacts.org

    What are the effects of eating only five days a week or following a fasting-mimicking diet five days a month? 
     
    Instead of eating every other day, what if you ate five days a week and fasted for the other two? As I discuss in my video The 5:2 Diet and the Fasting-Mimicking Diet Put to the Test, the available data are similar to that of alternate-day fasting: About a dozen pounds of weight loss was reported in overweight men and also reported in overweight women over six months, with no difference found between participants on the 5:2 intermittent fasting regimen and those on a continuous 500-calories-a-day restriction. The largest trial to date found an 18-pound weight loss within six months in the 5:2 group, which isn’t significantly different from the 20 pounds lost in the continuous calorie restriction group. Weight maintenance over the subsequent six months was also found to be no different.
     
    Though feelings of hunger may be more pronounced on the 5:2 pattern than on an equivalent level of daily calorie cutting, it does not seem to lead to overeating on non-fasting days. One might expect going two days without food may negatively impact mood, but no such adverse impact was noted for those fully fasting on zero calories or sticking to just two packets of oatmeal on each of the “fasting” days. (The oatmeal provides about 500 calories a day.) Like alternate-day fasting, the 5:2 fasting pattern appeared to have inconsistent effects on cognition and on preserving lean mass, and it also failed to live up to the “popular notion” that intermittent fasting would be “easier” to adhere to than daily calorie restriction. 
     
    Compared to those in the continuous-restriction control group, fewer subjects in the 5:2 pattern group expressed interest in continuing their diet after the study was over. This was attributed to quality-of-life issues, with 5:2 fasting participants citing headaches, lack of energy, and difficulty fitting the fasting days into their weekly routine. However, as you can see below and at 1:53 in my video, there has yet to be a single 5:2 diet study showing elevated LDL cholesterol compared with continuous calorie restriction at six months. Nor has it been shown for a year. This offers a potential advantage over alternate-day regimens. 

    Instead of 5:2, what about 25:5, spending five consecutive days a month on a “fasting-mimicking diet” (FMD)? Longevity researcher Valter Longo designed a five-day meal plan to try to simulate the metabolic effects of fasting by being low in protein, sugars, and calories with zero animal protein and zero animal fat. By making the diet plant-based, he hoped to lower the level of the cancer-promoting growth hormone IGF-1. He indeed accomplished this goal, along with a drop in markers of inflammation, after three cycles of his five-days-a-month program, as you can see below and at 2:33 in my video. 

    One hundred men and women were randomized to consume his fasting-mimicking diet for five consecutive days per month or maintain their regular diet the whole time. As you can see in the graph below and at 2:47 in my video, after three months, the FMD group was down about six pounds compared to the control group, with significant drops in body fat and waist circumference, accompanied by a drop in blood pressure. 

    Those who were the worst off accrued the most dramatic benefits, as seen in the graph below and at 3:04 in my video. What’s even wilder is that three further months after completion, some of the benefits appeared to persist, suggesting the effects “may last for several months.” It’s unclear, though, if those randomized to the FMD group used it as an opportunity to make positive lifestyle changes that helped maintain some of the weight loss. 


    Dr. Longo created a company to market his meal plan commercially, but, to his credit, says “he does not receive a salary or a consulting fee from the company…and will donate 100% of his shares to charity.” The whole diet appears to be mostly dehydrated soup mixes, herbal teas like hibiscus and chamomile, kale chips, nut-based energy bars, an algae-based DHA supplement, and a multivitamin dusted with vegetable powder. Why spend 50 dollars a day on a few processed snacks when you could instead eat a few hundred calories a day of real vegetables? 
     
    How interesting was that? All-you-can-eat above-ground vegetables for five days would have the same low amount of protein, sugars, and calories with zero animal protein or animal fat. But we’ll probably never know if it works as well, better, or worse because it’s hard to imagine such a study ever getting done without the financial incentive. 

    To learn more about IGF-1, see my video Flashback Friday: Animal Protein Compared to Cigarette Smoking.
     
    In this series on fasting, I’ve covered several topics, including the basics of calories and weight loss, water-only fasting, and the types of alternate-day fasting, see them all in the related videos below. 
     
    I close out the series with videos on time-restricted eating: Time-Restricted Eating Put to the Test and The Benefits of Early Time-Restricted Eating. 
     
    If you want all of the videos in one place, I’ve done three webinars on fasting—Intermittent Fasting, Fasting for Disease Reversal, and Fasting and Cancer—and they’re all available for download now. 

    Michael Greger M.D. FACLM

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  • Is Our Life Expectancy Extended by Intermittent Fasting?  | NutritionFacts.org

    Is Our Life Expectancy Extended by Intermittent Fasting?  | NutritionFacts.org


    Alternate-day modified fasting is put to the test for lifespan extension. 

    Is it true that alternate-day calorie restriction prolongs life? Doctors have anecdotally attributed improvements in a variety of disease states to alternate-day fasting, including asthma; seasonal allergies; autoimmune diseases, such as rheumatoid arthritis and osteoarthritis; infectious diseases, such as toenail fungus, periodontal disease, and viral upper respiratory tract infections; neurological conditions, such as Tourette’s syndrome and Meniere’s disease; atrial fibrillation; and menopause-related hot flashes. The actual effect on chronic disease, however, remains unclear, as I discuss in my video Does Intermittent Fasting Increase Human Life Expectancy?. 
     
    Alternate-day fasting has been put to the test for asthma in overweight adults, and researchers found that asthma-related symptoms and control significantly improved, as did the patients’ quality of life, including objective measurements of lung function and inflammation. As you can see in the graphs below and at 0:56 in my video, there were significant improvements in peak airflow, mood, and energy. Their weight also improved—about a 19-pound drop in eight weeks—so it’s hard to tease out the effects specific to the fasting beyond the benefits we might expect from weight loss by any means. 

    For the most remarkable study on alternate-day fasting, you have to go back more than a half-century. Though the 2017 cholesterol findings were the most concerning data I could find on alternate-day fasting, the most enticing was published in Spain in 1956. The title of the study translates as “The Hunger Diet on Alternate Days in the Nutrition of the Aged.” Inspired by the data being published on life extension with caloric restriction on lab rats, researchers split 120 residents of a nursing home in Madrid into two groups. Sixty residents continued to eat their regular diet, and the other half were put on an alternate-day modified fast. On the odd days of the month, they ate a regular 2,300-calorie diet; on the even days, they were given only a pound of fresh fruits and a liter of milk, estimated to add up to about 900 calories. This continued for three years. So, what happened? 
     
    As you can see below and at 2:16 in my video, throughout the study, 13 participants died in the control group, compared to only 6 in the intermittent fasting group, but those numbers were too small to be statistically significant. 

    What was highly significant, though, was the number of days spent hospitalized: Residents in the control group spent a total of 219 days in the infirmary, whereas the alternate-day fasting group only chalked up 123 days, as you can see below and at 2:38 in my video. 


    This is held up as solid evidence that alternate-day fasting may improve one’s healthspan and potentially even one’s lifespan, but a few caveats must be considered. It’s not clear how the residents were allocated to their respective groups. If, instead of being randomized, healthier individuals were inadvertently placed in the intermittent fasting group, that could skew the results in their favor. As well, it appears the director of the study was also in charge of medical decisions at the nursing home. In that role, he could have unconsciously been biased toward hospitalizing more folks in the control group. Given the progress that has been made in regulating human experimentation, it’s hard to imagine such a trial being run today, so we may never know if such impressive findings can be replicated. 

    Well, that was interesting! I had never even heard of that study until I started digging into the topic.  

    Check out my fasting series and popular videos on the subject here.  

    For more on longevity, see related videos below.





    Michael Greger M.D. FACLM

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  • How Safe Is Alternate-Day Intermittent Fasting?  | NutritionFacts.org

    How Safe Is Alternate-Day Intermittent Fasting?  | NutritionFacts.org


    Eating every other day can raise your cholesterol. 
     
    Are there any downsides to fasting every other day? For example, might go all day without eating impair your ability to think clearly? Surprisingly, as I discuss in my video Is Alternate-Day Intermittent Fasting Safe?, the results appear to be “equivocal.” Some studies show no measurable effects and the ones that do fail to agree on which cognitive domains are affected. Might the cycles of fasting and feasting cause eating disorder–type behaviors, like bingeing? So far, no harmful psychological effects have been found. In fact, there may be some benefit. However, the studies that have put it to the test specifically excluded those with a documented history of eating disorders, for whom the effects may differ. 
     
    What about bone health? No change in bone mineral density was noted after six months of alternate-day fasting despite about 16 pounds of weight loss, which would typically result in a dip in bone mass. However, the researchers did not note any skeletal changes in the control group either, and they lost a similar amount of weight using continuous caloric restriction. They suggested this is because both groups tended to be “more physically active than the average obese American,” getting about 1,000 to 2,000 more steps a day. 
     
    Proponents of intermittent fasting suggest it can better protect lean body mass, but most of the intermittent trials have employed less accurate methods of body composition analysis, whereas the majority of continuous caloric restriction trials used “vastly more accurate techniques.” So, to date, it is not clear if there’s a difference in lean mass preservation. 
     
    Improvements in blood pressure and triglycerides have been noted on intermittent fasting regimens, though this is presumed to be due to the reduction in body fat since the effect appears to be “dependent on the amount of weight lost.” Alternate-day fasting can improve artery function, too, as you can see in the graph below and at 1:55 in my video, though it does depend on what you’re eating on the non-fasting day. For study participants randomized to an alternate-day diet high in saturated fat, their artery function worsened despite a ten-pound weight loss, whereas it improved, as expected, in the lower-fat group. The decline in artery function was presumed to be because of the pro-inflammatory nature of saturated fat. 

    A concern has been raised about the effects of alternate-day fasting on cholesterol. After 24 hours without food, LDL cholesterol may temporarily bump up, but this is presumably because so much fat is being released into the system by the fast. As you can see in the graph below and at 2:33 in my video, an immediate negative effect on carbohydrate tolerance may stem from the same phenomenon—the repeated elevations of free fat floating around in the bloodstream. After a few weeks, though, LDL levels start to drop as the weight comes off. However, results from the largest and longest trial of alternate-day fasting have given me pause. 


    A hundred obese men and women were randomized into one of three groups: alternate-day modified fasting (25 percent of their baseline calories on fasting days and 125 percent calories on eating days), continuous, daily caloric restriction (75 percent of baseline), or a control group instructed to maintain their regular diet. So, for those going into the trial eating 2,000 calories a day, they would continue to eat 2,000 calories a day in the control group. The calorie-restriction group would get 1,500 calories every day, and the intermittent-restriction group would alternate between 500 calories a day and 2,500 calories the next. 
     
    As you can see in the graph below and at 3:32 in my video, with the same overall, average, prescribed calorie cutting in the two weight-loss groups, they both lost about the same amount of weight, but, surprisingly, the cholesterol effects were different. In the continuous calorie-restriction group, the LDL levels dropped as expected compared to the control group as the pounds came off. 

    But, in the alternate-day modified fasting group, they didn’t, as you can see below, and at 3:55 in my video. At the end of the year, the LDL cholesterol in the intermittent fasting group ended up being 10 percent higher than in the constant calorie-restriction group—despite the same loss of body fat. Given that LDL cholesterol is a prime causal risk factor for heart disease, our number one killer—or is even the prime risk factor—this strikes a significant blow against alternate-day fasting. If you want to try it anyway, I would advise you to have your cholesterol monitored to make sure it comes down with your weight. 


    If you’re diabetic, you must talk with your physician about medication adjustment for any changes in diet, including fasting of any duration. Even with proactive medication reduction, advice to immediately break the fast should sugars drop too low, and weekly medical supervision, people with type 2 diabetes who fasted for even just two days a week were twice as likely to suffer from hypoglycemic episodes compared to an unfasted control group. We still don’t know the best way to tweak blood sugar medications to prevent blood sugar from dropping too low on fasting days. 
     
    Even fasting for just one day can significantly slow the clearance of some drugs (like the blood-thinning drug Coumadin) or increase the clearance of others (like caffeine). Fasting for 36 hours can cut your caffeine buzz by 20 percent. So, consultation with your medical professional before fasting is an especially good idea for anyone on any kind of medication. 

    If you missed it, check out Alternate-Day Intermittent Fasting Put to the Test. 
     
    So, with ambiguous cognitive, lean mass, and bone effects, plus these cholesterol findings, I wouldn’t suggest alternate-day fasting for weight loss, but dropping pounds isn’t the only thing this way of eating is purported to do. Check out Does Intermittent Fasting Increase Human Life Expectancy?. 
     
    For other types of intermittent fasting, total fasting, and more on fasting, check out the related videos below. 





    Michael Greger M.D. FACLM

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  • Putting Alternate-Day Intermittent Fasting to the Test  | NutritionFacts.org

    Putting Alternate-Day Intermittent Fasting to the Test  | NutritionFacts.org


    Does eating every other day prevent the metabolic slowing that accompanies weight loss, or does it improve compliance over constant, day-to-day caloric restriction? 

    Rather than cutting calories day in and day out, what if you instead ate as much as you wanted every other day or for only a few hours a day? Or, what if you fasted two days a week or five days a month? These are all examples of intermittent fasting regimens, as you can see below and at 0:10 in my video Alternate-Day Intermittent Fasting Put to the Test, and that may even be how we were built. Three meals a day may be a relatively novel behavior for our species. For millennia, “our ancestors could not eat three meals every day. They consumed meals much less frequently, and often consumed one large meal per day or went for several days without food.” 

    Intermittent fasting is often presented as a means of stressing your body—in a good way. There is a concept in biology called hormesis, which can be thought of as the “that which doesn’t kill you makes you stronger” principle. Exercise is the classic example: You put stress on your heart and muscles, and as long as there is sufficient recovery time, you are all the healthier for it. Is that the case with intermittent fasting? Mark Twain thought so: “A little starvation can really do more for the average sick man than can the best medicines and the best doctors. I do not mean a restricted diet, I mean total abstention from food for one or two days.” 
     
    But, Twain also said, “Many a small thing has been made large by the right kind of advertising.” Is the craze over intermittent fasting just hype? Many diet fads have their roots “in legitimate science,” but over time, facts can get distorted, benefits exaggerated, and risks downplayed. In other words, “science takes a back seat to marketing.” At the same time, you don’t want to lose out on any potential benefit by dismissing something out of hand based on the absurdist claims of overzealous promoters. You don’t want to throw the baby out with the baby fat. 
     
    Religious fasting is the most studied form of intermittent fasting, specifically Ramadan, a month-long period in which “Muslims abstain from food and drink from sunrise until sunset.” The effects are complicated by a change in sleeping patterns and also thirst. The same dehydration issue arises with Yom Kippur when observant Jews stop eating and drinking for about 25 hours. The most studied form of intermittent fasting that deals only with food restriction is alternate-day fasting, which involves eating every other day, alternating with days consuming little or no calories. 
     
    At rest, we burn about a 50:50 mix of carbohydrates and fat, but we usually run out of glycogen—our carbohydrate stores—within 12 to 36 hours of stopping eating. At that point, our body has to shift to rely more on our fat stores. This metabolic switch may help explain why the greatest rate of breakdown and burning of fat over a three-day fast happens between hours 18 and 24 of the 72 hours. The hope is to reap some of the benefits of taking a break from eating without the risks of prolonged fasting. 
     
    One of the potential benefits of alternate-day fasting over chronic calorie restriction is that you get regular breaks from feeling constant hunger. But might people become so famished on their fasting day that they turn the next into a feasting day? After your fasting day, if you ate more than twice as much as you normally would, that presumably would defeat the whole point of alternate-day fasting. Mice fed every other day don’t lose weight. They just eat roughly twice as much food in one day as non-fasted mice would regularly eat in two days. That is not, however, what happens in people. 
     
    Study participants were randomized to fast for a day and a half—from 8:00 p.m. to 8:00 a.m. the second morning after beginning. Fasting for 36 hours only led to people eating an average of 20 percent more the day after they broke the fast, compared to a control group who didn’t fast at all. That would leave the fasters with a large calorie deficit, equivalent to a daily caloric restriction of nearly a thousand calories a day. This particular study involved lean men and women, but similar results have been found amongst overweight or obese subjects. Researchers typically found only about a 10 to 25 percent compensatory increase in calorie intake over baseline on non-fasting days, and this seems to be the case whether the fasting day was a true zero-calorie fast or a modified fast day of a few hundred calories, which may lead to better compliance. 
     
    Some studies have found that participants appeared to eat no more, or even eat less, on days after a day-long mini-fast. Even within studies, great variability is reported. In a 24-hour fasting study where individuals ate an early dinner and then had a late dinner the next day after skipping breakfast and lunch, the degree of compensation at the second dinner ranged from 7 percent to 110 percent, as you can see in the graph below and at 4:40 in my video. This means that some of the participants got so hungry by the time supper rolled around that they ate more than 24 hours’ worth of calories in a single meal. The researchers suggested that perhaps people first try “test fasts” to see how much their hunger and subsequent intake ramp up before considering an intermittent fasting regimen. Hunger levels can change over time, though, dissipating as your body habituates to the new normal. 


    In an eight-week study in which obese subjects were restricted to about 500 calories every other day, after approximately two weeks, they reportedly started feeling very little hunger on their slashed calorie days. This no doubt helped them lose about a dozen pounds on average over the duration of the study, but there was no control group with whom to compare. A similar study that did have a control group found a similar amount of weight loss—about ten pounds—over 12 weeks in a group of “normal weight” individuals, which means overweight on average. For these modified regimens where people are prescribed 500 calories on their “fasting” days, researchers found that, from a weight-loss perspective, it did not appear to matter whether those calories are divided up throughout the day or eaten in a single meal. 
     
    Instead of prescribing a set number of calories on “fasting” days, which many people find difficult to calculate outside of a study setting, a pair of Iranian researchers came upon a brilliant idea of unlimited above-ground vegetables. Starchy root vegetables are relatively calorie-dense compared to other vegetables. Veggies that grow above the ground include stem vegetables (like celery and rhubarb), flowering vegetables (like cauliflower), leafy vegetables (like, well, leafy vegetables), and all of the fruits we tend to think of as vegetables (like tomatoes, peppers, okra, eggplant, string beans, summer squash, and zucchini). So, instead of prescribing a certain number of calories for “fasting” days, researchers had subjects alternate between their regular diet and helping themselves to an all-you-can-eat, above-ground vegetable feast (along with naturally non-caloric beverages, like green tea or black coffee) every other day. After eight weeks, the subjects lost an average of 13 pounds and two inches off their waist, as you can see below and at 6:59 in my video. 


    The same variability discovered for calorie compensation has also been found for weight loss, as seen in the graph below and at 7:10 in my video. In a 12-month trial in which subjects were instructed to eat only one-quarter of their caloric needs every other day, weight changes varied from a loss of about 37 pounds to a gain of about 8 pounds. The biggest factor differentiating the low-weight-loss group from the high-weight-loss group appeared to be not how much they feasted on their regular diet days, but how much they were able to comply with the calorie restriction on their fast days. 

     
    Overall, ten out of ten alternate-day fasting studies showed significant reductions in body fat. Small short-term studies show about a 4 to 8 percent drop in body weight after 3 to 12 weeks. How does that compare with continuous calorie restriction? Researchers compared zero-calorie, alternate-day fasting head-to-head to a daily 400-calorie restriction for eight weeks. Both groups lost the same amount of weight, about 17 pounds, and, in the follow-up check-in six months later after the trial had ended, both groups had maintained a similar degree of weight loss; both were still down about a dozen pounds, as you can see below and at 8:10 in my video. 


    The hope that intermittent fasting would somehow avoid the metabolic adaptations that slow weight loss or improve compliance doesn’t seem to have materialized. The same compensatory reactions in terms of increased appetite and a slower metabolism plague both continuous and intermittent caloric restriction. The longest trial of alternate-day fasting found that “alternate-day fasting may be less sustainable” than more traditional approaches. By the end of the year, the drop-out rate of the alternate-day fasting group was 38 percent, compared to 29 percent in the continuous calorie-restriction group.  

    Although alternate-day fasting regimens haven’t been shown to produce superior weight loss to date, for individuals who may prefer this pattern of calorie restriction, are there any downsides? Find out in my video Is Alternate-Day Intermittent Fasting Safe?. 
     
    I packed a lot into this one. Bottom line: Fasting doesn’t appear to provide an edge over traditional calorie cutting, but if you prefer it, why not give fasting a try? Before you do, first check out Is Alternate-Day Intermittent Fasting Safe?.  

    What about total fasting? For that and even more, check out the related videos below.

    I have a whole chapter on intermittent fasting in my book How Not to Diet—order now! (All proceeds I receive from my books are donated to charity.) 





    Michael Greger M.D. FACLM

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  • The Safety of Fasting to Lose Weight  | NutritionFacts.org

    The Safety of Fasting to Lose Weight  | NutritionFacts.org

    Why should fasts lasting longer than 24 hours and particularly for three or more days only be done under the supervision of a health professional and preferably in a live-in clinic? 
     
    Fasting for a week or two can actually interfere with the loss of body fat, as shown at the start of my video Is Fasting for Weight Loss Safe?. But, eventually, after the third week of fasting, fat loss starts to overtake the loss of lean body mass in obese individuals, as seen in the graph below and at 0:14 in my video. Is it safe to go that long without food? 

    Proponents speak of fasting as a cleansing process, but some of what is being purged from our bodies are essential vitamins and minerals. People who are heavy enough can fast up to 382 days without calories, but no one can go even a fraction of that long without vitamins. Scurvy, for example, can be diagnosed within as few as four weeks without any vitamin C. Beriberi, deficiency of thiamine (vitamin B1), may start even earlier in fasting patients. And, once it manifests, it can result in brain damage within days, which can eventually become irreversible.  
     
    Even though fasting patients report problems such as nausea and indigestion after taking supplements, all of the months-long fasting cases I’ve discussed previously were given daily multivitamins and mineral supplementation as necessary. Without supplementation, hunger strikers and those undergoing prolonged fasts for therapeutic or religious purposes (like the Baptist pastor hoping “to enhance his spiritual powers for exorcism”) have ended up paralyzed, become comatose, or worse. 
     
    Nutrient deficiencies aren’t the only risk. After reading about all of the successful reports of massive weight loss from prolonged fasting in the medical literature, one doctor decided to give it a try with his patients. Of the first dozen he tried it on, two died. In retrospect, the two patients who died had started out with heart failure and had been on diuretics. Fasting itself produces pronounced diuresis, meaning loss of water and electrolytes through the urine, so it was the combination of fasting on top of the water pills that likely depleted their potassium and triggered their fatal heart rhythms. The doctor went out of his way to point out that both of the people who died started out “in severe heart failure, complicated by gross obesity; but both had improved greatly whilst undergoing starvation therapy.” That seems like a small consolation since they were both dead within a matter of weeks. 
     
    Not all therapeutic fasting fatalities were complicated by concurrent medication use, though. One researcher writes: “At first he did very well and experienced the usual euphoria…His pulse, blood pressure, and electrolytes remained satisfactory, but in the middle of the third week of treatment, he suddenly collapsed and died. This line of treatment is certainly tempting because it does produce weight loss and the patient feels so much better, but the report of case-fatalities”—the whole part about killing people—“must make it a very suspect line of management.” 
     
    Contrary to the popular notion that the heart muscle is specially spared during fasting, the heart appears to experience similar muscle wasting. This was “described in the victims of the Warsaw ghetto” during World War II in a remarkable series of detailed studies carried out by the ghetto physicians before they themselves succumbed. In a case entitled “Gross Fragmentation of Cardiac Fiber After Therapeutic Starvation for Obesity,” a 20-year-old woman successfully “achieved her ideal weight” after losing 128 pounds by fasting for 30 weeks. “After a breakfast of one egg,” she had a heart attack and died. On autopsy, as you can see below and at 3:44 in my video, the muscle fibers in her heart showed evidence of widespread disintegration. The pathologists suggested that fasting regimens “should no longer be recommended as a safe means of weight reduction.” 
    Breaking the fast appears to be the most dangerous part. After World War II, as many as one out of five starved Japanese prisoners of war tragically died following liberation. Now known as “refeeding syndrome,” multiorgan system failure can result from resuming a regular diet too quickly. This is because there are critical nutrients such as thiamine and phosphorus that are used to metabolize food. Therefore, in the critical refeeding window, if too much food is taken before these nutrients can be replenished, demand may exceed supply. Whatever residual stores you still carry can be driven down even further, with potentially fatal consequences. This is why rescue workers are taught to always give thiamine before food to victims who have been trapped or otherwise unable to eat. Thiamine is responsible for the yellow color of “banana bags,” a term you might have heard used in medical dramas to describe an IV fluid concoction often given to malnourished alcoholics to prevent a similar reaction. (You can see a photo of them below and at 4:53 in my video.) Anyone “with negligible food intake for more than five days” may be at risk of developing refeeding problems. 
    Medically-supervised fasting has gotten much safer now that there are proper refeeding protocols. We now know what warning signs to look for and who shouldn’t be fasting in the first place, such as those who have advanced liver or kidney failure, porphyria, uncontrolled hyperthyroidism, and pregnant and breastfeeding women. The most comprehensive safety analysis of medically supervised, water-only fasting was recently published by the TrueNorth Health Center in California. Out of 768 visits to its facility for fasts up to 41 days, were there any adverse events? There were 5,961 of them! Most of these were mild, known reactions to fasting, such as fatigue, nausea, insomnia, headache, dizziness, upset stomach, and back pain. Only two serious events were reported, and no fatalities. You can see the chart below and at 5:58 in my video. 
    “Fasting periods lasting longer than 24 hr, and particularly those lasting 3 or more days, should be done under the supervision of a physician and preferably in a [live-in] clinic.” In other words, don’t try this at home! This is not just legalistic mumbo-jumbo. For example, normally, your kidneys dive into sodium conservation mode during fasting, but should that response break down, you could rapidly develop an electrolyte abnormality that may only manifest with non-specific symptoms, like fatigue or dizziness, which could easily be dismissed until it’s too late. 
     
    The risks of any therapy must be premised on the severity of the disease. The consequences of obesity are considered so serious that effective therapies could have “considerable acceptable toxicity.” For example, many consider major surgery for obesity to be a justifiable risk, but the keyword is effective. 
     
    Therapeutic fasting for obesity has largely been abandoned by the medical community not only because of its uncertain safety profile but its questionable short- and long-term efficacy. Remember, for a fast that only lasts a week or two, you might be able to lose as much body fat or even more on a low-calorie diet than a no-calorie diet. 
     
    Fasting for a week or two can actually interfere with the loss of body fat. For more background on this, see Is Fasting Beneficial for Weight Loss? and Benefits of Fasting for Weight Loss Put to the Test.
     
    If you’re wondering what the best way to lose weight is, I wrote a whole book about it! Check out How Not to Diet. 
     
    Interested in learning more about fasting? See related videos below. 

    Michael Greger M.D. FACLM

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  • Does Fasting Benefit Weight Loss?  | NutritionFacts.org

    Does Fasting Benefit Weight Loss?  | NutritionFacts.org

    Like the keto diet, fasting for one or two weeks can actually slow the loss of body fat rather than accelerate it.

    Fasting obviously causes consistent, dramatic weight loss, as shown in the graph below and at 0:09 in my video Is Fasting Beneficial for Weight Loss?, but how do fasted individuals do long-term? Some research groups reported “extremely disappointing long-term effects,” as you can see in the graph below and at 0:19 in my video. 

    Average subjects started at about 270 pounds and, in the six months before the fast, continued to gain weight as obese persons tend to do. After 24 days of “inpatient starvation,” they experienced a dramatic 27-pound weight loss. Then, what do you think happened?

    They gained it all back and more, though one could argue if they had not fasted, they might have weighed even more at that point, as seen in the graph below and at 0:45 in my video. 
    In another study with follow-ups ranging up to 50 months, only 4 out of 25 “superobese” patients achieved even partial sustained success. Based on these kinds of data, some investigators “concluded that complete starvation is of no value in the long-term treatment of obese patients.” 
     
    Other research teams reported better outcomes. One series with about 100 individuals found that 60 percent retained at least some weight loss at follow-up or even continued losing. The follow-up periods varied from 1 to 32 months with no breakdown as to who fasted and for how long, though, making the data hard to interpret. In another study, 62 patients were down an average of 16 pounds after fasting for 10 days. After one year, 40 percent of the group had retained at least 7 pounds of that weight loss. 
     
    As you can see below and at 1:37 in my video, when you put together six such studies, hundreds of obese subjects fasted for an average of 44 days and lost an average of 52 pounds. And, around one or two years later, 40 percent retained at least some of that weight loss. So, most gained back all of the weight they had lost, but 40 percent is extraordinary for a weight-loss study. 

    Following a hundred obese individuals getting treated at a weight-loss clinic with a standard low-calorie diet, researchers found that only one out of a hundred lost more than 40 pounds and only about one in ten lost even 20 pounds, with overall successful weight maintenance at only two patients over two years, as seen below and at 2:08 in my video. That’s why having a control group is so important. What may look like a general failure may actually be a relative success compared to more traditional weight-loss techniques. 

    Researchers new to the field may find it “clearly disappointing” that the “overall results of follow-up for 12 months or more” found that “two-thirds of the patients were ‘failures’ and more than one-third actually regained all the weight lost.” But, 12 percent were labeled successes, maintaining 59 pounds of weight loss two years later. As you can see in the graph below and at 2:42 in my video, the subjects lost massive amounts of excess weight and kept it off. 

    In a direct comparison of different weight-loss approaches at the same clinic, five years after initiating a conventional low-calorie approach, only about one in five was down 20 pounds compared to nearly half in the group who instead had undergone a few weeks of fasting years previously. By year seven, as you can see in the graph below and at 3:03 in my video, most of those instructed on daily caloric restriction were back up to their original weight or had even exceeded it, but that was only true for about one in ten in the fasted group. In an influential paper in the New England Journal of Medicine on seven myths about obesity, fallacy number three was identified as: “Large, rapid weight loss is associated with poorer long-term weight-loss outcomes, as compared with slow, gradual weight loss.” In reality, the opposite is true. The hare may end up skinnier than the turtle.  

    As shown in the graph below and at 3:39 in my video, researchers set up a study comparing the sustainability of weight loss at three different speeds: six days of fasting, three weeks on a very-low-calorie diet of 600 calories a day, or six weeks on a low-calorie diet of 1,200 calories a day. 

    The question is: What happened a year later? At one year, the fasting group was the only one that sustained a significant loss of weight, as you can see below and at 3:55 in my video. 

    What happened nine years later? “Therapeutic Fasting in Morbid Obesity” is the largest, longest follow-up study I could find. At least some of the fast-induced weight losses were maintained a year later by the great majority. After one year, 90 percent remained lighter than they had started, but after two years, three years, four years, and seven years, fewer and fewer patients maintained their weight loss. By nine years later, that number dropped to fewer than one in ten. By then, almost everyone had regained the weight they had initially fasted away, as you can see in the graph below and at 4:17 in my video. “Many patients thought that the temporary loss was worth the effort,” though. As a group, they had lost an average of about 60 pounds. They described improved health and quality of life and claimed that “reemployment was facilitated and earnings increased” during that period of time. But the fasting didn’t appear to result in any permanent change in eating habits for the vast majority. 
    The small minority for whom fasting led to sustainable weight loss “all admit to a radical change in previous eating habits”; indeed, fasting only works long-term if it can act as a jumpstart to a healthier diet. In a retrospective long-term comparison of weight reduction after an inpatient stay at a naturopathic center, those who fasted lost more weight at the time, but they were back to the same weight at around seven years, as you can see in the graph below and at 5:14 in my video. 

    It’s no surprise since most reported returning to the same diet they had been on before. However, those who were placed instead on a healthier, more whole food, plant-based diet were more likely to make persistent changes in their eating and, seven years later, were lighter than when they started, as you can see in the graph below and at 5:36 in my video. 

    Why can’t you have it both ways, though? Use fasting to kickstart a big drop, then start a healthier diet. The problem is that the big drop is largely illusory, as you can see in the graph below and at 5:48 in my video. 

    Fasting for a week or two can cause more weight loss than caloric restriction, but, paradoxically, it may actually lead to less loss of body fat. How can eating fewer calories lead to less fat loss? Because during fasting, your body starts cannibalizing itself and burning more of your own protein for fuel. Emperor penguins, elephant seals, and hibernating bears can survive by just burning fat without dipping into their muscles, but our voracious big brains appear to need at least a trickle of blood sugar. If we aren’t eating any carbohydrates, our body is forced to start turning our protein into sugar to burn. Even getting just a few grams of carbs—from adding honey to water when fasting, for instance—can cut protein loss up to 50 percent.  

    What about adding exercise to prevent the loss of lean tissues during a fast? That may make it worse! At rest, most of your heart and muscle energy needs can be met with fat, but if you start exercising, some of the blood sugar meant for your brain starts getting snatched up and your body may have to break down even more protein. 
     
    As you can see in the graph below and at 7:00 in my video, less than half of the weight loss during the first few weeks of fasting ends up coming from your fat stores. So, even if you double your daily weight loss on a fast, you may be actually losing less body fat. 

    In an NIH-funded study, obese individuals were placed on an 800-calorie-a-day diet for two weeks and steadily lost about a pound of body fat a day. They were then switched to about two weeks of zero calories and started losing more protein and water. On average, though, they only lost a few ounces of fat daily. When they were subsequently switched back to the initial 800-calories-a-day diet for a week, they rapidly replaced the protein and water, so the scale registered their weight as going up, but their body fat loss accelerated back to the approximate pound a day. The scale made it look as though they were doing better when they were completely fasting, but the reality is they were doing worse. So, during the five-week experiment, they would have lost even more body fat had they stuck with their calorie-restricted diet rather than completely stopping eating in the middle. They would have lost more body fat by eating more calories. Fasting for a week or two can interfere with the loss of body fat, rather than accelerate it. You can see a series of graphs depicting this from 7:13 in my video, including the one below. 

    This is the follow-up to Benefits of Fasting for Weight Loss Put to the Test. It seems fasting may only work long-term if it can act as a jumpstart to a healthier diet, and just fasting for a week or two can be counterproductive, like the keto diet. Is it even safe to fast longer than that? Find out in Is Fasting for Weight Loss Safe?. 
     
    For more on the keto story and more on fasting for weight loss, see related videos below. 
     
    I’ve done my third live webinar on fasting, Fasting and Cancer. Those videos are also on NutritionFacts.org. 

    Michael Greger M.D. FACLM

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  • Putting the Benefits of Fasting for Weight Loss to the Test  | NutritionFacts.org

    Putting the Benefits of Fasting for Weight Loss to the Test  | NutritionFacts.org

    For more than a century, fasting has been used as a weight-loss treatment.

    I’ve talked about the benefits of caloric restriction. Well, the greatest caloric restriction is getting no calories at all. Fasting has been branded “the next big weight loss fad,” but it has a long history throughout various spiritual traditions, practiced by Moses, Jesus, Muhammed, and Buddha. In 1732, a noted physician wrote, “He that eats till he is sick must fast till he is well.” About one in seven American adults today report taking that advice, “using fasting as a means to control body weight,” as I discuss in my video Benefits of Fasting for Weight Loss Put to the Test. 
     
    Case reports of the treatment of obesity through fasting date back more than a century in the medical literature. In 1915, two Harvard doctors indelicately described “two extraordinarily fat women,” one of whom “was a veritable pork barrel.” Their success led them to conclude that “successive moderate periods of starvation constitute a perfectly safe, harmless, and effective method for reducing the weight of those suffering from obesity.” 
     
    The longest-recorded fast, published in 1973, made it into the Guinness Book of World Records. To reach his ideal body weight, a 27-year-old man fasted for 382 days straight, losing 276 pounds, and managed to keep nearly all of it off. He was given vitamin and mineral supplements so he wouldn’t die, but no calories for more than a year. In the researchers’ acknowledgments, they thanked him “for his cheerful co-operation and steadfast application to the task of achieving a normal physique.” 
     
    In a U.S. Air Force study, more than 20 individuals at least 100 pounds overweight and most “unable to lose weight on previous diets” were fasted for as long as 84 days. Nine dropped out of the study, but the 16 who remained “were unequivocally successful” at losing 40 to 100 pounds. In the first four days, the subjects were noted as losing as much as four pounds a day, which “probably represents mostly fluid,” mostly water weight as the body starts to adapt. But, after a few weeks, they were steadily losing about a pound a day of mostly straight fat. The investigator described the starvation program as “a dramatic and exciting treatment for obesity.” 
     
    Of course, the single most successful diet for weight loss—namely no diet at all—is also the single least sustainable. What other diet can cure morbid obesity in a matter of months but practically be guaranteed to kill you within a year if you stick with it? The reason diets don’t work, almost by definition, is that people go on them, then they go off of them. Permanent weight loss is only achieved through permanent lifestyle change. So, what’s the point of fasting if you’re just going to go back to your regular diet and gain right back all of that lost weight? 
     
    Fasting proponents cite the psychological benefit of realigning people’s perceptions and motivation. Some individuals have resigned themselves to the belief that weight loss for them is somehow impossible. They may think “that they are ‘made differently’ from those of normal weight” in some way, and no matter what they do, the pounds don’t come off. But the rapid, unequivocal weight loss during fasting demonstrates to them that with a large enough change in eating habits, it’s not just possible, but inevitable. This morale boost may then embolden them to make better food choices once they resume eating. 
     
    The break from food may allow some an opportunity “to pause and reflect” on the role food is playing in their lives—not only the power it has over them but the power they have over it. In a fasting study entitled “Correction and Control of Intractable Obesity,” a patient’s personality was described as changing “from one of desperation, with abandonment of hope, to that of an eager extravert full of plans for a promising future.” She realized that her weight was within her own power to control. The researchers concluded: “This highly intellectual social worker has been returned to a full degree of exceptional usefulness.” 
     
    After a fast, newfound commitment to more healthful eating may be facilitated by a reduction in overall appetite reported post-fast, compared to pre-fast, at least temporarily. Even during a fast, hunger may start to dissipate within the first 36 hours. So, challenging people’s delusions about their exceptionality to the laws of physics—thinking they are “made differently”—with “short periods of total fasting may seem barbaric. In reality, this method of weight reduction is remarkably well tolerated by obese patients.” That seems to be a recurring theme in these published series of cases. In the influential paper “Treatment of Obesity by Total Fasting for up to 249 Days,” the researchers remarked that the “most surprising aspect of this study was the ease with which the prolonged fast was tolerated.” All of their patients “spontaneously commented on their increased sense of well-being, and in some, this amounted to frank euphoria.” They continued that, although “treatment by total fasting must only be prescribed under close medical supervision,” they “are convinced that it is the treatment of choice, certainly in cases of gross obesity.” 
     
    Fasting for a day can make people irritable and feel moody and distracted, but after a few days of fasting, many report feeling clear, elated, and alert—even euphoric. This may be in part due to the significant rise in endorphins that accompanies fasting, as you can see in the graph below and at 5:48 in my video. Mood enhancement during fasting is thought to perhaps represent an adaptive survival mechanism to motivate the food search. This positive outlook towards the future may then facilitate the behavioral change necessary to lock in some of the weight-loss benefits. 

    Is that what happens, though? Is fasting actually effective over the long term? There are articles with titles like “Death During Therapeutic Starvation for Obesity.” Is fasting even safe? We’ll find out next. 
     
    This is the sixth in a 14-part series on fasting for weight loss. In case you missed any of the others, see the related videos below. 

    My book How Not to Diet is all about weight loss. You can learn more about it and order it here. 

    Michael Greger M.D. FACLM

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  • Any Pitfalls with Restricting Calories?  | NutritionFacts.org

    Any Pitfalls with Restricting Calories?  | NutritionFacts.org

    How may we preserve bone and mass on a low-calorie diet? 
     
    One of the most consistent benefits of calorie restriction is that blood pressure improves in as little as one or two weeks. Blood pressure may even be normalized in a matter of weeks and blood pressure pills discontinued. Unfortunately, this can work a little too well and cause orthostatic intolerance, which can manifest as lightheadedness or dizziness upon standing and, in severe cases, may cause fainting, though staying hydrated can help. 
     
    What about loss of muscle mass? In the CALERIE trial, which I profile in my video Potential Pitfalls of Calorie Restriction, 70 percent of the body weight the subjects lost was fat and 30 percent was lean body mass. So, they ended up with an improved body composition of about 72 percent lean mass compared to 66 percent in the control group, as you can see at 0:51 in my video. And, even though leg muscle mass and strength declined in absolute terms, relative to their new body size, they generally got stronger. 

    Is there any way to preserve even more lean mass, particularly among older individuals who naturally tend to lose muscle mass with age? Increased protein intakes are commonly suggested, but most studies fail to find a beneficial effect on preserving muscle strength or function whether you’re young or old, active or sedentary. For example, during a 25 percent calorie restriction, researchers randomized overweight older men and women to either a normal-protein diet with 4 grams for every ten pounds of body weight or a high-protein diet with about 8 grams per ten pounds. That doubling of protein intake had no discernible effect on lean body mass, muscle strength, or physical performance. As you can see below and at 1:48 in my video, most such studies found the same lack of benefit, but when they’re all put together, one can tease out a small advantage of about one or two pounds of lean mass over an average of six months. 

    Unfortunately, high protein intake during weight loss has also been found to have “profound” negative metabolic effects, including undermining the benefits of weight loss on insulin sensitivity. As you can see in the graph below and at 2:14 in my video, if you lose 20 pounds, you can dramatically improve your body’s ability to handle blood sugars, compared to subjects in a control group who maintained their weight. But, if you lose the exact same amount of weight on a high-protein diet, getting about an extra 30 grams a day, it’s like you never lost any weight at all. 


    Though you can always bulk back up after weight loss, the best way to preserve muscle mass during weight loss is to exercise. The CALERIE study had no structured exercise component, and, similar to bariatric surgery, about 30 percent of the weight loss was lean mass. In contrast, that proportion was only about 16 percent of The Biggest Loser contestants, chalked up to their “vigorous exercise program.” Resistance training even just three times a week can prevent more than 90 percent of lean body mass loss during calorie restriction. 
     
    The same may be true of bone loss. Lose weight through calorie restriction alone, and you experience a decline in bone mineral density in fracture risk sites, such as the hip and spine. In the same study, though, those randomized to lose weight with exercise did not suffer any bone loss. The researchers concluded: “Our results suggest that regular EX [exercise] should be included as part of a comprehensive weight loss program to offset the adverse effects of CR [caloric restriction] on bone.” 
     
    It’s hard to argue with calls for increased physical activity, but even without an exercise regimen, the “very small” drop in bone mineral density in the CALERIE trial might only increase a ten-year risk of osteoporotic fracture by about 0.2 percent. The benefits of calorie restriction revealed by the study included improvements in blood pressure and cholesterol, as you can see in the graph below and at 3:54 in my video, as well as improved mood, libido, and sleep. These would seem to far outweigh any potential risks. The fact that a reduction in calories seemed to have such wide-ranging benefits on quality of life led commentators in the AMA’s internal medicine journal to write: “The findings of this well-designed study suggest that intake of excess calories is not only a burden to our physical homeostasis [or equilibrium], but also on our psychological well-being.” 
     


    Check out my other videos on calorie restriction, fasting, intermittent fasting, and time-restricted eating in the related videos below. 

     

    Michael Greger M.D. FACLM

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  • Restricting Calories for Longevity?  | NutritionFacts.org

    Restricting Calories for Longevity?  | NutritionFacts.org

    Though a bane for dieters, a slower metabolism may actually be a good thing.

    We’ve known for more than a century that calorie restriction can increase the lifespan of animals, and metabolic slowdown may be the mechanism. That could be why the tortoise lives ten times longer than the hare. Rabbits can live for 10 to 20 years, whereas “Harriet,” a tortoise “allegedly collected from the Galapagos Islands by Charles Darwin, was estimated to be about 176 years old when she died in 2006.” Slow and steady may win the race. 
     
    As I discuss in my video The Benefits of Calorie Restriction for Longevity, one of the ways our body lowers our resting metabolic rate is by creating cleaner-burning, more efficient mitochondria, the power plants that fuel our cells. It’s like our body passes its own fuel-efficiency standards. These new mitochondria create the same energy with less oxygen and produce less free radical “exhaust.” After all, when our body is afraid famine is afoot, it tries to conserve as much energy as it can. 
     
    Indeed, the largest caloric restriction trial to date found metabolic slowing and a reduction in free radical-induced oxidative stress, both of which may slow the rate of aging. The flame that burns twice as bright burns half as long. But, whether this results in greater human longevity is an unanswered question. Caloric restriction is often said “to extend lifespan in every species studied,” but that isn’t even true of all strains within a single species. Two authors of one article, for instance, don’t even share the same view: One doesn’t think calorie restriction will improve human longevity at all, while the other suggests that a 20 percent calorie restriction starting at age 25 and sustained for 52 years could add five years onto your life. Either way, the reduced oxidative stress would be expected to improve our healthspan. 
     
    Members of the Calorie Restriction Society, self-styled CRONies (for Calorie-Restricted Optimal Nutrition), appear to be in excellent health, but they’re a rather unique, self-selected group of individuals. You don’t really know until you put it to the test. Enter the CALERIE study, the Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy, the first clinical trial to test the effects of caloric restriction. 
     
    Hundreds of non-obese men and women were randomized to two years of 25 percent calorie restriction. They only ended up achieving half that, yet they still lost about 18 pounds and three inches off their waists, wiping out more than half of their visceral abdominal fat, as you can see in the graph below and at 2:47 in my video. 

    That translated into significant improvements in cholesterol levels, triglycerides, insulin sensitivity, and blood pressure, which you can see in the graph below and at 2:52 in my video. Eighty percent of those who were overweight when they started were normal-weight by the end of the trial, “compared with a 27% increase in those who became overweight in the control group.” 

    In the famous Minnesota Starvation Study that used conscientious objectors as guinea pigs during World War II, the study subjects suffered both physically and psychologically, experiencing depression, irritability, and loss of libido, among other symptoms. The participants started out lean, though, and had their calorie intake cut in half. The CALERIE study ended up being four times less restrictive, only about 12 percent below baseline calorie intake, and enrolled normal-weight individuals, which in the United States these days means overweight on average. As such, the CALERIE trial subjects experienced nothing but positive quality-of-life benefits, with significant improvements in mood, general health, sex drive, and sleep. They only ended up eating about 300 fewer calories a day than they had eaten at baseline. So, they got all of these benefits—the physiological benefits and the psychological benefits—just from cutting about a small bag of chips’ worth of calories from their daily diets. 
     
    What happened at the end of the trial, though? As researchers saw in the Minnesota Starvation Study and in calorie deprivation experiments done on Army Rangers, as soon as the subjects were released from restriction, they tended to rapidly regain the weight and sometimes even more, as you can see below and at 4:18 in my video. 

    The leaner they started out, the more their bodies seemed to drive them to overeat to pack back on the extra body fat, as seen in the graph below and at 4:27 in my video. In contrast, after the completion of the CALERIE study, even though their metabolism was slowed, the participants retained about 50 percent of the weight loss two years later. They must have acquired new eating attitudes and behaviors that allowed them to keep their weight down. After extended calorie restriction, for example, cravings for sugary, fatty, and junky foods may actually go down. 
    This is part of my series on calorie restriction, intermittent fasting, and time-restricted eating. See related videos below.

    Michael Greger M.D. FACLM

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  • The New Rule for Calories per Pound of Weight Loss  | NutritionFacts.org

    The New Rule for Calories per Pound of Weight Loss  | NutritionFacts.org

    You may lose a pound of fat by skipping just 10 calories a day or as many as 55, depending on whether you’re improving food quality or restricting food quantity. 
     
    If the 3,500 calories per pound of weight loss rule is bunk, what’s the alternative? To lose a pound of fat, how many fewer calories do you have to eat or how many more do you have to burn? That’s the topic of my video The New Calories per Pound of Weight Loss Rule. 
     
    There are validated mathematical models that take into account the dynamic changes that occur when you cut calories, such as the metabolic slowdown, and they’ve been turned into free online calculators you can use to make personalized estimates. For instance, one is the Body Weight Planner from the National Institutes of Health (http://bit.ly/NIHcalculator) and another is the Pennington Biomedical Research Center’s Weight Loss Predictor Calculator out of Louisiana State University (http://bit.ly/LSUcalculator). 
     
    The NIH Body Weight Planner has been found to be more accurate because the LSU model appears to overestimate the drop in physical activity, but they both have their own pluses and minuses. The NIH Body Weight Planner tells you how many calories you need to restrict and/or how much more you need to exercise to achieve a specific weight-loss goal by a specific date. If you click on the “Switch to Expert Mode” button, you can get a graph and exportable chart showing your day-to-day weight-loss trajectory. See below and at 1:15 in my video to see the Body Weight Planner. 

    For instance, if you are a middle-aged, sedentary, average-height woman who is obese at 175 pounds and wants to be closer to her ideal weight within a year, consuming 2,000 calories a day would prevent future weight gain and taking in about 1,400 calories a day would bring down your weight, and you could maintain that lower weight at 1,700 calories a day. If you also walked a mile a day, you’d have a little more calorie leeway.

    The LSU Weight Loss Predictor, however, doesn’t allow you to tweak physical activity, but its advantage is that you don’t have to choose a goal or time frame. Just put in different calorie changes, and it graphs out your expected course, as you can see in the graph below and at 2:00 in my video. 

    Is there an easy rule of thumb you can use? Yes. Every permanent ten-calorie drop in daily intake will eventually lead to about one pound of weight loss, though it takes about a year to achieve half the total weight change and around three years to completely settle into the new weight. So, cutting 500 calories a day can cause the 50-pound weight loss predicted by the 3,500-Calorie Rule, but that’s the total weight loss at which you plateau, not an annual drop, and it takes about three years to get there. A 500-calorie deficit would be expected to cause about a 25-pound weight loss in the first year, followed by an additional 25 pounds lost over years two and three, but that’s only if you can maintain the 500-calorie deficit, as you can see in the graph below and at 2:38 in my video.


    If you’re eating the same diet that led to the original weight problem but just in smaller servings, you should expect your appetite to rev up by about 45 calories per pound lost. So, if you were cutting 500 calories a day through portion control alone, even before you were down a dozen pounds, you’d feel so famished that you’d be driven to eat 500 more calories a day and your weight loss could vanish. For this reason, if you’re dead set on eating the same diet with the same foods, just in smaller quantities, you have to cut down an additional 45 calories per pound of desired weight loss to offset your hunger drive. 
     
    So, to take off that one pound, instead of consuming just 10 fewer calories a day using the 10 Calories per Pound Rule, you’d have to eat 10 fewer calories on top of the 45 fewer calories to account for the revving up of your appetite. Thus, it would be 10 + 45 = 55 fewer calories. Indeed, just by changing diet quantity and not quality, it takes 55 fewer calories per day to lose a pound, so that daily 500-calorie deficit would only net you about a 9-pound weight loss over time instead of 50 pounds. That’s why portion control methods can be such a frustrating failure for so many people. 
     
    If you missed my first two videos on calories per pound, check out The 3,500 Calorie per Pound Rule Is Wrong and The Reason Weight Loss Plateaus When You Diet. 
     
    I have loads of other weight-loss videos, which you can see here on the topic page, and there are gazillions more coming soon, based on my book How Not to Diet.

    Michael Greger M.D. FACLM

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  • Why Weight Loss Plateaus on Diets  | NutritionFacts.org

    Why Weight Loss Plateaus on Diets  | NutritionFacts.org

    What are the metabolic and behavioral adaptations that slow weight loss? 
     
    Thanks to millions of years of evolution hard-wiring us to survive scarcity, our body has compensatory survival mechanisms to defend against weight loss. When we start losing weight, we may unconsciously begin to move less as a “behavioral adaptation” to conserve energy. There are metabolic adaptations as well; our metabolism slows down. Every pound of weight loss may reduce our resting metabolic rate by seven calories a day. This may only translate to a few percent differences for most, but it can rapidly snowball for those who achieve massive weight loss. I discuss this phenomenon in my video The Reason Weight Loss Plateaus When You Diet.

    During one season of the television show The Biggest Loser, some of the contestants famously had their metabolic rates tracked. As you can see in the graphs below, above and beyond the hundreds of fewer calories it takes to just exist when more than a hundred pounds lighter (at 0:55 in my video), by the end of the season, their metabolic rates had slowed by an extra 500 calories a day (at 1:03 in my video). 

    What’s mind-blowing is that when they were retested six years later, they still had the 500-calorie-a-day handicap. So, the contestants had to cut 500 more calories than anyone else their size to maintain the same weight loss. No wonder the bulk of their weight loss was regained. As you can see in the graph below and at 1:23 in my video, most remained at least 10 percent lower than their starting weight, though. 

    Even a 7 percent drop has been shown to cut diabetes rates about in half, as seen in the graph below and at 1:31 in my video. Still, the metabolic slowing means you have to work that much harder than everyone else just to stay in place. Analyzing four seasons of The Biggest Loser minute-by-minute, researchers noted that 85 percent of the focus was on exercise rather than diet, though the exercise component accounted for less than half of the weight loss. Even six years after their season ended, the contestants had been maintaining an hour of daily, vigorous exercise, yet still regained most of the weight they had lost. Why? Because they had started eating more. They could have limited their exercise to just 20 minutes a day and still maintained 100 percent of their initial weight loss if they had just been able to keep their intake to less than 3,000 calories a day. That may not sound like much of a challenge, but weight loss doesn’t just slow your metabolism. It also boosts your appetite.

    If it were just a matter of your weight settling at the point at which your reduced caloric intake matches your reduced caloric output, it would take years for your weight loss to plateau. Instead, it often happens within six to eight months. You can see illustrative graphs below and at 2:34 and 2:43 in my video. You may know the drill: Start the diet, stick to the diet, then weight loss stalls six months later. What happened? Don’t blame your metabolism—that only plays a small part. Instead, you likely stopped sticking to your diet because your appetite went on a rampage. 

    Let’s break it down. If you cut 800 calories out of your daily diet—going from 2,600 calories a day down to 1,800, for instance—and your weight loss stalls after six months, what may have happened is, at the end of the first month, you think you’re still cutting 800 calories, but you may actually only be down about 600 calories a day. By month two, you may only be down about 500 calories, 300 by month three, and, by month six, you may only be eating 200 calories less than before you went on the diet. In other words, you may have inadvertently suffered an exponential increase in caloric intake over those six months. But, you may not even realize it because, by that time, your body may have ramped up your appetite by 600 calories. So, it still feels as if you are eating 800 calories less, but it’s actually only 200 fewer calories. Since an 800-calorie drop in intake may slow your metabolism and physical activity by about 200 calories a day, with no difference between calories in and calories out at six months, no wonder your weight loss grinds to a complete halt.

    The slow upward drift in caloric intake on a new diet is not because you got lazy. Once your appetite is boosted by 600 calories after dieting for a while, eating 200 fewer calories at the end is as hard as eating 800 fewer calories at the beginning. So, you can maintain the same disciplined level of willpower and self-control yet still end up stagnating. To prevent this from happening, you need to maintain the calorie deficit. How is that possible in the face of a ravenous appetite? 
     
    Hunger is a biological drive. Asking someone to eat smaller portions is like asking someone to take fewer breaths. You can white-knuckle it for a bit, but, eventually, nature wins out. That’s why I wrote How Not to Diet. There are foods that can counter the slowing of our metabolism and suppress our appetite, as well as ways of eating to counter the behavioral adaptation and even eat more food—yet still lose weight. 
     
    Due to “the ongoing slowing of metabolism and increased appetite associated with the lost weight,” sustained weight loss requires a persistent calorie deficit of 300 to 500 calories a day. This can be accomplished without reducing portion sizes simply by lowering the calorie density of meals, which can result in the rare combination of weight loss with both an increase in quality and even quantity of food consumed. (See the two graphs below and at 5:34 and 5:40 in my video.) The bottom line is that sustainable weight loss is not about eating less food. It’s about eating better food.

    In my previous video, I dive into how The 3,500 Calorie per Pound Rule Is Wrong. In that case, what’s The New Calories per Pound of Weight Loss Rule? Watch that video to find out. 
     
    My book How Not to Diet is all about weight loss and how to break the diet cycle. For more on weight loss, see related videos below.

    See the Weight Loss topic page for more relevant videos. 

    Michael Greger M.D. FACLM

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  • Debunking the 3,500-Calorie-per-Pound Rule  | NutritionFacts.org

    Debunking the 3,500-Calorie-per-Pound Rule  | NutritionFacts.org

    How many fewer calories do you have to eat every day to lose one pound of body fat? 

    The first surgical attempt at body sculpting was in 1921 on a dancer “who wanted to improve the shape of her ankles and knees.” The surgeon apparently scraped away too much tissue and tied the stitches too tight, resulting in necrosis, amputation, and the first recorded malpractice suit in the history of plastic surgery. Liposuction is much safer today, killing only about 1 in 5,000 patients, mostly from unknown causes, such as throwing a clot into your lung or perforating your internal organs. You can see a “Cause of Death” chart below and at 0:37 in my video The 3,500 Calorie per Pound Rule Is Wrong. 

    Liposuction currently reigns as the most popular cosmetic surgery in the world, and its effects are indeed only cosmetic. A study published in the New England Journal of Medicine assessed obese women before and after having about 20 pounds of fat sucked out of their bodies, resulting in a nearly 20 percent drop in their total body fat. Normally, if you lose even just 5 to 10 percent of your body weight in fat, you get significant improvements in blood pressure, blood sugars, inflammation, cholesterol, and triglycerides. But liposuction sucks. None of those benefits materialized even after massive liposuction, which suggests that the problem is not subcutaneous fat, the fat under our skin. The metabolic insults of obesity arise from the visceral fat, the fat surrounding or even infiltrating our internal organs, like the fat marbling our muscles and liver. The way you lose that fat, the dangerous fat, is to take in fewer calories than you burn. 
     
    Anyone who’s seen The Biggest Loser television programs knows that with enough caloric restriction and exercise, hundreds of pounds can be lost. Similarly, there are cases in the medical literature of what some refer to as “super obesity.” In one case, a man lost a massive amount of weight “largely without professional help and without surgery” and kept it off for years. He dropped 374 pounds, losing about 20 pounds a month by cycling two hours a day and reducing his daily intake to 800 calories, which is down around what some prisoners got at concentration camps in World War II. 
     
    Perhaps “America’s most celebrated weight loss” seen on television was Oprah’s. She pulled out a wagon full of fat, representing the 67 pounds she had lost on a very-low-calorie diet. How many calories did she have to cut to achieve that weight loss within four months? If you consult with leading nutrition textbooks or refer to trusted authorities like the Mayo Clinic, you’ll learn the simple weight loss rule: 1 pound of fat equals 3,500 calories. Quoting from the Journal of the American Medical Association, “A total of 3500 calories equals 1 pound of body weight. This means if you decrease (or increase) your intake by 500 calories daily, you will lose (or gain) 1 pound per week. (500 calories per day × 7 days = 3500 calories.)” 
     
    It’s the simple weight-loss rule that is simply not true. 
     
    The 3,500-calorie rule can be traced back to a paper published in 1958. The author noted that since fatty tissue in the human body is 87 percent fat, a pound of body fat would have about 395 grams of pure fat. Multiplying that by nine calories per gram of fat gives you that “3,500 calories per pound” approximation. The fatal flaw that leads to “dramatically exaggerated” weight-loss predictions is that the 3,500-calorie rule fails to take into account the fact that changes in the Calories-In side of the energy-balance equation automatically lead to changes in the Calories-Out side—for example, metabolic adaption, the slowing of metabolic rate that accompanies weight loss. That’s one reason weight loss plateaus. 
     
    Imagine a sedentary, 30-year-old woman of average height who weighs 150 pounds. According to the 3,500-calorie rule, if she cuts 500 calories out of her daily diet, she’d lose a pound a week or 52 pounds a year. In three years, she would vanish. She’d go from 150 pounds to -6. Obviously, that doesn’t happen. Instead, as you can see in the graph below and at 4:33 in my video, in the first year, she’d likely lose 32 pounds, not 52. Then, after a total of three years, she’d probably stabilize at about 100 pounds. This is because it takes fewer calories to exist as a thin person.  


    Part of it is “simple mechanics”: More energy is required to move a heavier mass, in the same way a Hummer requires more fuel than a compact car. Think how much more effort it would take to just get up from a chair, walk across the room, or climb a few stairs if you were carrying a 50-pound backpack. Even when you’re at rest, sound asleep, there’s simply less of your body to maintain as you lose weight. Every pound of fat tissue lost may mean one less mile of blood vessels through which your body has to pump blood every minute. So, the basic upkeep and movement of thinner bodies take fewer calories. As you lose weight by eating less, you end up needing less. That’s what the 3,500-calorie rule doesn’t take into account. 
     
    Imagine it another way: A 200-pound man starts consuming 500 more calories a day, maybe by drinking a large soda or eating two donuts. According to the 3,500-calorie rule, in ten years, he’d weigh more than 700 pounds. That doesn’t happen because, the heavier he is, the more calories he burns just by existing. If you’re 100 pounds overweight, it’s as if there’s a skinny person inside you trying to walk around balancing 13 gallons of oil or lugging around a sack filled with 400 sticks of butter. As you can see in the graph below and at 6:13 in my video, it takes about two donuts’ worth of extra energy just to live at 250 pounds, so that’s where you’d plateau if you kept it up. Given a certain calorie excess or deficit, weight gain or weight loss is a curve that flattens out over time, rather than a straight line up or down. 


    Nevertheless, the 3,500-calorie rule continues to crop up, even in obesity journals. Public health researchers used it to calculate how many pounds children might lose every year if, for example, fast-food kids’ meals swapped in apple slices for french fries. You can see the “Counting Calories in Kids’ Meals” graphic below and at 6:39 in my video. 

    They figured that two meals a week could add up to about four pounds a year. The actual difference, National Restaurant Association–funded researchers were no doubt delighted to point out, would probably add less than half a pound—ten times less than the 3,500-calorie rule would predict, as you can see below and at 7:06 in my video. That original article was subsequently retracted. 

     
    The 3,500 Calorie per Pound Rule Is Wrong is the first of 14 videos that are part of my fasting series, about which I did two webinars. The videos are on NutritionFacts.org, or you can get them all now in a digital download at Intermittent Fasting. You may also be interested in my webinars on Fasting and Disease Reversal and Fasting and Cancer.

    Other videos in this series are included in related videos below. 
     
    Check out some other popular videos on weight loss.

    I also recently tackled the ketogenic diet.

    Michael Greger M.D. FACLM

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