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  • 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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  • Does Black Cumin Seed (Nigella Sativa) Help with Weight Loss?  | NutritionFacts.org

    For three cents a day, black cumin may improve our cholesterol and triglyceride levels, blood pressure, and blood sugar control, as well as accelerate the loss of body fat.

    Black cumin, also known as Nigella sativa or simply “black seed,” is not related to cumin; it’s a member of the buttercup family rather than the carrot family. Black cumin, with its peppery flavor, is a spice commonly used in Indian and Middle Eastern cuisines, but it’s also been prized for its purported medicinal benefits. Described as “a miracle herb,” with mentions going back to the Old Testament, it was found cached in King Tut’s tomb, and it’s been reported that the “Islamic prophet Muhammad once stated that the black seed can heal every disease except death.” Only in the last 50 years or so has it been put to the test, though, culminating in more than a thousand papers published in the medical literature.

    Typical doses used in studies are one or two grams a day, which is only about a quarter teaspoon. This enables researchers to perform randomized, double-blind, placebo-controlled trials by putting the whole-food spice powder into capsules rather than studying a component or extract.

    A systematic review and meta-analysis of randomized, placebo-controlled trials found that daily black cumin consumption significantly improves cholesterol and triglycerides. Researchers also found that it not only improves blood pressure, but it also improves blood sugar control. Some of the results are quite extraordinary. For example, one study found that postmenopausal women randomized to a gram a day (less than a quarter teaspoon) of black cumin powder reduced their LDL cholesterol by 27 percent within two months, significantly better than placebo. Those are the kinds of results we’d expect from a statin drug, yet it was achieved with just a sprinkle’s worth of a simple spice. Black cumin may also help with menopausal symptoms.

    Now, it doesn’t appear to cure anything—a month after stopping the spice, cholesterol levels began to creep back up, for instance, as you can see below and at 2:00 in my video Benefits of Black Cumin Seed (Nigella Sativa) for Weight Loss—but it does appear to be a cheap, safe, effective, and delicious (if you like spice) treatment for some of our deadliest risk factors. And its side effects include loss of appetite and weight loss! 

    The latest systematic review and meta-analysis of randomized controlled weight-loss trials found that about a quarter teaspoon of black cumin powder a day does appear to cause weight loss within a span of a few months. If it really can benefit so many facets of health, why don’t we hear more about it? Why wasn’t I taught about it in medical school? Maybe because there’s little profit motive. Black cumin is just a common, natural spice. The daily dose used in most of these studies would cost about three cents a day. Stockholders won’t be thrilled to sell something that can’t be patented and costs only three pennies a day. Black cumin has become a staple in my family’s daily diet. I keep a pepper mill filled with it right on the kitchen table and grind it onto foods just as I would black pepper—easy and delicious.

    Michael Greger M.D. FACLM

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  • Eat Quinoa and Lower Triglycerides? | NutritionFacts.org

    Eat Quinoa and Lower Triglycerides? | NutritionFacts.org

    How do the nutrition and health effects of quinoa compare to other whole grains?

    “Approximately 90% of the world’s calories are provided by less than one percent of the known 250,000 edible plant species.” The big three are wheat, corn, and rice, and our reliance on them may be unsustainable, given the ongoing climate crisis. This has spurred new interest in “underutilized crops,” like quinoa, which might do better with drought and heat.

    Quinoa has only recently been introduced into the Northern Hemisphere, but humans have been eating quinoa for more than 7,000 years. Is there any truth to its “superfood” designation, or is it all just marketing hooey?

    Quinoa is a “pseudograin,” since the plant it comes from isn’t a type of grass. “Botanically speaking quinoa is an achene, a seed-like fruit with a hard coat,” and it has a lot of vitamins and minerals, but so do all whole grains. It also has a lot of protein. As you can see below and in a series of graphs starting at 1:05 in my video Benefits of Quinoa for Lowering Triglycerides, quinoa has more protein than other grains, but since when do we need more protein? Fiber is what we’re sorely lacking, and its fiber content is relatively modest, compared to barley or rye. Quinoa is pretty strong on folate and vitamin E, though, and it leads the pack on magnesium, iron, and zinc. So, it is nutritious, but when I think superfood, I think of something with some sort of special clinical benefit. Broccoli is a superfood, strawberries are a superfood, and so is garlic, but quinoa? Consumer demand is up, thanks in part to “perceived health benefits,” and it has all sorts of purported benefits in lab animals, but there have been very few human studies. 

    The first trial was a before-and-after study of quinoa granola bars that showed drops in triglycerides and cholesterol, as you can see below and at 1:53 in my video, but it didn’t have a control group, so we don’t know how much of that would have happened without the quinoa. The kind of study I want to see is a randomized controlled trial. When researchers gave participants about a cup of cooked quinoa every day for 12 weeks, they experienced a 36 percent drop in their triglycerides. That’s comparable to what one gets with triglyceride-lowering drugs or high-dose fish oil supplements.

    Which is better, regular quinoa or red quinoa? As you can see in the graph below and at 2:22 in my video, the red variety has about twice the antioxidant power, leading the investigators to conclude that red quinoa “might…contribute significantly to the management and/or prevention of degenerative diseases associated with free radical damage,” but it’s never been put to the test. 

    What about black quinoa? Both red and black quinoa appear to be equally antioxidant-rich, both beating out the more conventional white variety, as you can see in the graph below and at 2:46 in my video. 

    The only caveat I could find is to inform your doctor before your next colonoscopy or else they might mistake quinoa for parasites. As reported in a paper, a “colonoscopy revealed numerous egg-like tan-yellow ovoid objects, 2 to 3 mm in diameter, of unclear cause,” but they were just undigested quinoa.

    For more on the superfoods I mentioned, check the related posts below.

    Isn’t fish oil important to heart health? Find out in my video Is Fish Oil Just Snake Oil?.

    Michael Greger M.D. FACLM

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  • Syncing Your Brain and Body Clocks  | NutritionFacts.org

    Syncing Your Brain and Body Clocks  | NutritionFacts.org

    Exposure to bright light synchronizes the central circadian clock in our brain, whereas proper meal timing helps sync the timing of different clock genes throughout the rest of our body. 
     
    One of the most important breakthroughs in recent years has been the discovery of “peripheral clocks.” We’ve known for decades about the central clock—the so-called suprachiasmatic nucleus. It sits in the middle of our brain right above the place where our optic nerves cross, allowing it to respond to day and night. Now we also know there are semi-autonomous clocks in nearly every organ of our body. Our heart runs on a clock, our lungs run on one, and so do our kidneys, for instance. In fact, up to 80 percent of the genes in our liver are expressed in a circadian rhythm.

    Our entire digestive tract is, too. The rate at which our stomach empties, the secretion of digestive enzymes, and the expression of transporters in our intestinal lining for absorbing sugar and fat all cycle around the clock. So, too, does the ability of our body fat to sop up extra calories. The way we know these cycles are driven by local clocks, rather than being controlled by our brain, is that you can take surgical biopsies of fat, put them in a petri dish, and watch them continue to rhythm away.

    All of this clock talk is not just biological curiosity. Our health may depend on keeping all of them in sync. “Imagine a child playing on a swing.” Picture yourself pushing, but you become distracted by what’s going on around you in the playground and stop paying attention to the timing of the push. So, you forget to push or you push too early or too late. What happens? Out of sync, the swinging becomes erratic, slows, or even stops. That is what happens when we travel across multiple time zones or have to work the night shift.

    The “pusher” in this case is the light cues falling onto our eyes. Our circadian rhythm is meant to get a “push” from bright light every morning at dawn, but if the sun rises at a different time or we’re exposed to bright light in the middle of the night, this can push our cycle out of sync and leave us feeling out of sorts. That’s an example of a mismatch between the external environment and our central clock. Problems can also arise from a misalignment between the central clock in our brain and all the other organ clocks throughout our body. An extreme illustration of this is a remarkable set of experiments suggesting that even our poop can get jet lag.

    As you can see below and at 2:31 in my video How to Sync Your Central Circadian Clock to Your Peripheral Clocks, our microbiome seems to have its own circadian rhythm.

    Even though the bacteria are down where the sun doesn’t shine, there’s a daily oscillation in both bacterial abundance and activity in our colon, as you can see in the graph below and at 2:43 in my video. Interesting, but who cares? We all should. 

    Check this out: If you put people on a plane and fly them halfway around the world, then feed their poop to mice, those mice grow fatter than mice fed preflight feces. The researchers suggest the fattening flora was a consequence of “circadian misalignment.” Indeed, several lines of evidence now implicate “chronodisruption”—the state in which our central and peripheral clocks diverge out of sync—as playing a role in conditions such as premature aging and cancer, as well as ranging to others like mood disorders and obesity.

    Exposure to bright light is the synchronizing swing pusher for our central clock. What drives our internal organ clocks that aren’t exposed to daylight? Food intake. That’s why the timing of our meals may be so important. Researchers removed all external timing cues by keeping study participants under constant dim light and found that you could effectively decouple central rhythms from peripheral ones just by shifting meal times. They took blood draws every hour and biopsies of the subjects’ fat every six hours to demonstrate the resulting metabolic disarray.

    Just as morning light can help sync the central clock in our brain, morning meals can help sync our peripheral clocks throughout the rest of our body. Skipping breakfast disrupts the normal expression and rhythm of these clock genes themselves, which coincides with adverse metabolic effects. Thankfully, they can be reversed. Take a group of habitual breakfast-skippers and have them eat three meals at 8:00 am, 1:00 pm, and 6:00 pm, and their cholesterol and triglycerides improve, compared to taking meals five hours later at 1:00 pm, 6:00 pm, and 11:00 pm. There is a circadian rhythm to cholesterol synthesis in the body, too, which is also “strongly influenced by food intake.” This is evidenced by the 95 percent drop in cholesterol production in response to a single day of fasting. That’s why a shift in meal timing of just a few hours can result in a 20-point drop in LDL cholesterol, thanks to eating earlier meals, as you can see below and at 5:00 in my video. 

    If light exposure and meal timing help keep everything synced, what happens when our circumstances prevent us from sticking to a normal daytime cycle? We’ll find out in The Metabolic Harms of Night Shifts and Irregular Meals. If you’re just coming into the series, be sure to check out the related posts 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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  • 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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  • 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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