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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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  • Sugar and Gaining Weight  | NutritionFacts.org

    Sugar and Gaining Weight  | NutritionFacts.org

    The sugar industry responds to evidence implicating sweeteners in the obesity epidemic. 
     
    In terms of excess body fat, the “well-documented obesity epidemic may merely be the tip of the overfat iceberg.” It’s been estimated that 91 percent of adults—nine out of ten of us—and 69 percent of children in the United States are overfat, a condition defined as having “excess body fat sufficient to impair health.” This can occur even in individuals who are “normal-weight and non-obese, often due to excess abdominal fat.” The way to tell if you’re overfat is if your waist circumference is more than half your height. What’s causing this epidemic? As I discuss in my video Does Sugar Lead to Weight Gain?, one primary cause may be all the added sugars we’re eating. 
     
    A century ago, sugar was heralded as one of the cheapest forms of calories in the diet. Just ten cents’ worth of sugar could furnish thousands of calories. Dr. Fredrick Stare, “Harvard’s sugar-pushing nutritionist,” bristled at the term “empty calories,” writing that the calories in sugar were “not empty but full of energy”—in other words, full of calories, which we are now getting too much of. The excess bodyweight of the U.S. population corresponds to about a daily 350- to 500-calorie excess on average. So, “to revert the obesity epidemic,” that’s how many calories we have to reduce, but which calories should we cut? As you can see below and at 1:33 in my video, the majority of Americans who fail to meet the Dietary Guidelines’ sugar limit get about that many calories in added sugars every day: Twenty-five teaspoons’ worth of added sugars is about 400 calories. 

    There are die-hard sugar defenders. James Rippe, for example, was reportedly paid $40,000 a month by the high fructose corn syrup industry—and that was on top of the $10 million it paid for his research. Even Dr. Rippe considers it “undisputable that sugars…contribute to obesity. It is also undisputable that sugar reduction…should be part of any weight loss program.” And, of all sources of calories to limit, since sugar is just empty calories and contains no essential nutrients, “reducing sugar consumption is obviously the place to start.” And, again, this is what the researchers funded by the likes of Dr. Pepper and Coca-Cola are saying. The primary author of “Dietary Sugar and Body Weight: Have We Reached a Crisis in the Epidemic of Obesity and Diabetes?…,” Richard Kahn, is infamous for his defense of the American Beverage Association—the soda industry—and he was the chief science officer at the American Diabetes Association when it signed a million-dollar sponsorship deal with the world’s largest candy company. “Maybe the American Diabetes Association should rename itself the American Junk Food Association,” said the director of a consumer advocacy group. What do you expect from an organization that was started with drug industry funding? 
     
    The bottom line is that “randomised controlled trials show that increasing sugars intake increases energy [calorie] intake” and “increasing sugar intake leads to body weight gain in adults, and…sugar reduction leads to body weight loss in children.” For example, when researchers randomized individuals to either increase or decrease their intake of table sugar, the added sugar group gained about three and a half pounds over ten weeks, whereas the reduced sugar group lost about two and a half pounds. A systematic review and meta-analysis of all such ad libitum diet studies—real-life studies where sugar levels were changed but people could otherwise eat whatever they wanted—found that reduced intake of dietary sugars resulted in a decrease in body weight, whereas “increased sugars intake was associated with a comparable weight increase.” The researchers found that, “considering the rapid weight gain that occurs after an increased intake of sugars, it seems reasonable to conclude that advice relating to sugars intake is a relevant component of a strategy to reduce the high risk of overweight and obesity in most countries.” That is, it’s reasonable to advise people to cut down on their sugar consumption. 
     
    Findings from observational studies have been “more ambiguous,” though, with an association found between obesity and intake of sweetened beverages, but failing to show consistent correlations with consumption of sugary foods. Most such studies rely on self-reported data, however, and “it is likely that this has introduced bias, especially as underreporting of diet has been found to be more prevalent among obese people and it is sugar-rich foods that are most commonly underreported.” However, one can measure trace sucrose levels in the urine, which gives an objective measure of actual sugar intake and also excludes contributions from other sweeteners such as high fructose corn syrup. When researchers did this, they discovered that, indeed, sugar intake is not only associated with greater odds of obesity and greater waist circumference on a snapshot-in-time cross-sectional basis, but that was also seen in a prospective cohort study over time. “Using urinary sucrose as the measure of sucrose intake,” researchers found that “participants in the highest v. the lowest quintile [fifth] for sucrose intake had 54% greater risk of being overweight or obese.” 
     
    “Denying evidence that sugars are harmful to health has always been at the heart of the sugar industry’s defense.” But when the evidence is undeniable, like the link between sugar and cavities, it switches from denial to deflection, like trying to pull attention away from restricting intake to coming up with some kind of “vaccine against tooth decay.” We seem to have reached a similar point with obesity, with the likes of the Sugar Bureau switching from denial to deflection by commissioning research suggesting that obese individuals would not benefit from losing weight, a stance contradicted by hundreds of studies across four continents involving more than ten million participants. 
     
    For more on Big Sugar’s influence, check out Sugar Industry Attempts to Manipulate the Science. 
     
    You may also be interested in some of my other popular videos on sugar. 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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  • Keto Diets and Diabetes  | NutritionFacts.org

    Keto Diets and Diabetes  | NutritionFacts.org

    Ketogenic diets are put to the test for diabetes reversal. 
     
    As you can see at the start of my video Does a Ketogenic Diet Help Diabetes or Make It Worse?, ketogenic diets can lower blood sugars better than conventional diets. So much so, in fact, that there is a keto product company that claims ketogenic diets can “reverse” diabetes. However, they are confusing the symptom (high blood sugars) with the disease (carbohydrate intolerance). People with diabetes can’t properly handle carbohydrates, and this manifests as high blood sugars. Clearly, if you stick to eating mostly fat, your blood sugars will stay low, but you may be actually making the underlying disease worse at the same time. 
     
    We’ve known for nearly a century that if you put people on a ketogenic diet, their carbohydrate intolerance can skyrocket within just two days. Below and at 0:46 in my video, you can see a graph from the study showing the blood sugar response two days after eating sugar. On a high-carb diet, blood sugar response is about 90 mg/dL. But, the blood sugar response to the same amount of sugar after a high-fat diet is about 190 mg/dL, nearly double. The intolerance to carbohydrates skyrocketed on a high-fat diet. 

    After one week on an 80 percent fat diet, you can quintuple your blood sugar spike in reaction to the same carb load compared to a week on a low-fat diet, as you can see in the graph below and at 1:12 in my video. 

    Even a single day of excessive dietary fat intake can do it, as you can see in the graph below and at 1:26 in my video. If you’re going in for a diabetes test, having a fatty dinner the night before can adversely affect your results. Just one meal high in saturated fat can make carbohydrate intolerance, the cause of diabetes, worse within four hours. 


    Given enough weight loss by any means, whether from cholera or bariatric surgery, type 2 diabetes can be reversed, but a keto diet for diabetes may not just be papering over the cracks, but actively throwing fuel on the fire. 
     
    I’ve been trying to think of a good metaphor. It’s easy to come up with things that just treat the symptoms without helping the underlying disease, like giving someone with pneumonia aspirin for their fever instead of antibiotics. However, a keto diet for diabetes is worse than that because it may treat the symptoms while actively worsening the disease. It may be more like curing the fever by throwing that pneumonia patient out into a snow bank or “curing” your amputated finger by amputating your hand. One of the co-founders of masteringdiabetes.org suggested it’s like a CEO who makes their bad bottom line look better by borrowing tons of cash. The outward numbers look better, but on the inside, the company is just digging itself into a bigger hole. 
     
    Do you remember The Club, that popular car anti-theft device that attaches to the steering wheel and locks it in place so the steering column can only turn a few inches? Imagine you’re in a car at the top of a hill with the steering wheel locked. Then, the car starts rolling down the hill. What do you do? Imagine there’s also something stuck under your brake pedal. The keto-diet equivalent response to this situation is who cares if you’re barreling down into traffic with a locked steering wheel and no brakes—just stick to really straight deserted roads without any stop signs or traffic lights. If you do that, problem solved! The longer you go, the more speed you’ll pick up. If you should hit a dietary bump in the road or start to veer off the path, the consequences could get more and more disastrous over time. However, if you stick to the keto straight and narrow, you’ll be a-okay! In contrast, the non-keto response would be to just unlock the steering wheel and dislodge whatever’s under your brake. In other words, fix the underlying problem instead of just whistling past—and then into—the graveyard. 
     
    The reason keto proponents claim they can “reverse” diabetes is they can successfully wean type 2 diabetics off their insulin. That’s like faith-healing someone out of the need for a wheelchair by making them stay in bed the rest of their life. No need for a wheelchair if you never move. Their carbohydrate intolerance isn’t gone. Their diabetes isn’t gone. In fact, it could be just as bad or even worse. Type 2 diabetes is reversed when you are weaned off insulin while eating a normal diet like everyone else. Then and only then do you not have diabetes anymore. A true diabetes reversal diet, as you can see below and at 4:58 in my video, is practically the opposite of a ketogenic diet: getting diabetics off their insulin within a matter of weeks by eating more than 300 grams of carbs a day! 
    The irony doesn’t stop there. One of the reasons people with diabetes suffer such nerve and artery damage is due to an inflammatory metabolic toxin known as methylglyoxal, which forms at high blood sugar levels. Methylglyoxal is the most potent creator of advanced glycation end products (AGEs), which are implicated in degenerative diseases—from Alzheimer’s and cataracts to kidney disease and strokes, as you can see below and at 5:31 in my video. 

    You get AGEs in your body from two sources: You can eat them preformed in your diet or make them internally from methylglyoxal if you have high blood sugar levels. On a keto diet, one would expect high exposure to preformed AGEs, since they’re found concentrated in animal-derived foods high in fat and protein, but we would expect less internal, new formation due to presumably low levels of methylglyoxal, given lower blood sugars from not eating carbs. Dartmouth researchers were surprised to find more methylglyoxal! As shown in the graph below and at 6:11 in my video, a few weeks on the Atkins diet led to a significant increase in methylglyoxal levels. Those in active ketosis did even worse, doubling the level of this glycotoxin in their bloodstream. 

    It turns out that high sugars may not be the only way to create this toxin, as you can see below and at 6:24 in my video. One of the ketones you make on a ketogenic diet is acetone (known for its starring role in nail polish remover). Acetone does more than just make keto dieters fail breathalyzer tests, “feel queasy and light-headed, and develop what’s been described as ‘rotten apple breath.’” Acetone can oxidize in the blood to form acetol, which may be a precursor for methylglyoxal.

    That may be why keto dieters can end up with levels of this glycotoxin as high as those with out-of-control diabetes, which can cause the nerve damage and blood vessel damage you see in diabetics. That’s another way keto dieters can end up with a heart attack. The irony of treating diabetes with a ketogenic diet may extend beyond just making the underlying diabetes worse, but by mimicking some of the disease’s dire consequences. 

    This is part of a seven-video series on keto, which you can find in related videos below.

    I also recently tackled diabetes.

    Michael Greger M.D. FACLM

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  • Muscle Shrinkage and Bone Loss on Keto Diets?  | NutritionFacts.org

    Muscle Shrinkage and Bone Loss on Keto Diets?  | NutritionFacts.org

    Ketogenic diets have been found to undermine exercise efforts and lead to muscle shrinkage and bone loss. 
     
    An official International Society of Sports Nutrition position paper covering keto diets notes the “ergolytic effect” of keto diets on both high- and low-intensity workouts. Ergolytic is the opposite of ergogenic. Ergogenic means performance-boosting, whereas ergolytic means performance-impairing. 
     
    For nonathletes, ketosis may also undermine exercise efforts. Ketosis was correlated with increased feelings of “perceived exercise effort” and “also significantly correlated to feelings of ‘fatigue’ and to ‘total mood disturbance,’” during physical activity. “Together, these data suggest that the ability and desire to maintain sustained exercise might be adversely impacted in individuals adhering to ketogenic diets for weight loss.” 
     
    You may recall that I’ve previously discussed that shrinkage of measured muscle mass among CrossFit trainees has been reported. So, a ketogenic diet may not just blunt the performance of endurance athletes, but their strength training as well. As I discuss in my video Keto Diets: Muscle Growth and Bone Density, study participants performed eight weeks of the battery of standard upper and lower body training protocols, like bench presses, pull-ups, squats, and deadlifts, and there was no surprise. You boost muscle mass—unless you’re on a keto diet, in which case there was no significant change in muscle mass after all that effort. Those randomized to a non-ketogenic diet added about three pounds of muscle mass, whereas the same amount of weight lifting on the keto diet tended to subtract muscle mass by about 3.5 ounces on average. How else could you do eight weeks of weight training and not gain a single ounce of muscle on a ketogenic diet? Even keto diet advocates call bodybuilding on a ketogenic diet an “oxymoron.” 
     
    What about bone loss? Sadly, bone fractures are one of the side effects that disproportionately plague children placed on ketogenic diets, along with slowed growth and kidney stones. Ketogenic diets may cause a steady rate of bone loss as measured in the spine, presumed to be because ketones are acidic, so keto diets can put people in what’s called a “chronic acidotic state.” 
     
    Some of the case reports of children on keto diets are truly heart-wrenching. One nine-year-old girl seemed to get it all, including osteoporosis, bone fractures, and kidney stones, then she got pancreatitis and died. Pancreatitis can be triggered by having too much fat in your blood. As you can see in the graph below and at 2:48 in my video, a single high-fat meal can cause a quintupling of the spike in triglycerides in your bloodstream within hours of consumption, which can put you at risk for inflammation of the pancreas.  

    The young girl had a rare genetic disorder called glucose transporter deficiency syndrome. She was born with a defect in ferrying blood sugar into her brain. That can result in daily seizures starting in infancy, but a ketogenic diet can be used as a way to sneak fuel into the brain, which makes a keto diet a godsend for the 1 in 90,000 families stricken with this disorder.

    As with anything in medicine, it’s all about risks versus benefits. As many as 30 percent of patients with epilepsy don’t respond to anti-seizure drugs. Unfortunately, the alternatives aren’t pretty and can include brain surgery that implants deep electrodes through the skull or even removes a lobe of your brain. This can obviously lead to serious side effects, but so can having seizures every day. If a ketogenic diet can help with seizures, the pros can far outweigh the cons. For those just choosing a diet to lose weight, though, the cost-benefit analysis would really seem to go the other way. Thankfully, you don’t need to mortgage your long-term health for short-term weight loss. We can get the best of both worlds by choosing a healthy diet, as I discussed in my video Flashback Friday: The Weight Loss Program That Got Better with Time.
     
    Remember the study that showed the weight loss was nearly identical in those who had been told to eat the low-carb Atkins diet for a year and those told to eat the low-fat Ornish diet, as seen below and at 4:18 in my video? The authors concluded, “This supports the practice of recommending any diet that a patient will adhere to in order to lose weight.” That seems like terrible advice. 

    There are regimens out there like “The Last Chance Diet which consisted of a low-calorie liquid formula made from leftover byproducts from a slaughterhouse [that] was linked to approximately 60 deaths from cardiovascular-related events.” An ensuing failed lawsuit from one widower laid the precedent for the First Amendment protection for those who produce deadly diet books. 

    It’s possible to construct a healthy low-carb diet or an unhealthy low-fat one—a diet of cotton candy would be zero fat—but the health effects of a typical low-carb ketogenic diet like Atkins are vastly different from a low-fat plant-based diet like Ornish’s. As you can see in the graph below and at 5:26 in my video, they would have diametrically opposed effects on cardiovascular risk factors in theory, based on the fiber, saturated fat, and cholesterol contents of their representative meal plans. 

    And when actually put to the test, low-carb diets were found to impair artery function. Over time, blood flow to the heart muscle itself is improved on an Ornish-style diet and diminished on a low-carb one, as shown below and at 5:44 in my video. Heart disease tends to progress on typical weight-loss diets and actively worsens on low-carb diets, but it may be reversed by an Ornish-style diet. Given that heart disease is the number one killer of men and women, “recommending any diet that a patient will adhere to in order to lose weight” seems irresponsible. Why not tell people to smoke? Cigarettes can cause weight loss, too, as can tuberculosis and a meth habit. The goal of weight loss is not to lighten the load for your pallbearers. 

     
    For more on keto diets, see my videos on the topic. Interested in enhancing athletic performance? Check out the related videos below. 

    Michael Greger M.D. FACLM

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  • The Safety of Keto Diets  | NutritionFacts.org

    The Safety of Keto Diets  | NutritionFacts.org

    What are the effects of ketogenic diets on nutrient sufficiency, gut flora, and heart disease risk? 

    Given the decades of experience using ketogenic diets to treat certain cases of pediatric epilepsy, a body of safety data has accumulated. Nutrient deficiencies would seem to be the obvious issue. Inadequate intake of 17 micronutrients, vitamins, and minerals has been documented in those on strict ketogenic diets, as you can see in the graph below and at 0:14 in my video Are Keto Diets Safe?. 

    Dieting is a particularly important time to make sure you’re meeting all of your essential nutrient requirements, since you may be taking in less food. Ketogenic diets tend to be so nutritionally vacuous that one assessment estimated that you’d have to eat more than 37,000 calories a day to get a sufficient daily intake of all essential vitamins and minerals, as you can see in the graph below and at 0:39 in my video. 


    That is one of the advantages of more plant-based approaches. As the editor-in-chief of the Journal of the American Dietetic Association put it, “What could be more nutrient-dense than a vegetarian diet?” Choosing a healthy diet may be easier than eating more than 37,000 daily calories, which is like putting 50 sticks of butter in your morning coffee. 
     
    We aren’t just talking about not reaching your daily allowances either. Children have gotten scurvy on ketogenic diets, and some have even died from selenium deficiency, which can cause sudden cardiac death. The vitamin and mineral deficiencies can be solved with supplements, but what about the paucity of prebiotics, the dozens of types of fiber, and resistant starches found concentrated in whole grains and beans that you’d miss out on? 
     
    Not surprisingly, constipation is very common on keto diets. As I’ve reviewed before, starving our microbial self of prebiotics can have a whole array of negative consequences. Ketogenic diets have been shown to “reduce the species richness and diversity of intestinal microbiota,” our gut flora. Microbiome changes can be detected within 24 hours of switching to a high-fat, low-fiber diet. A lack of fiber starves our good gut bacteria. We used to think that dietary fat itself was nearly all absorbed in the small intestine, but based on studies using radioactive tracers, we now know that about 7 percent of the saturated fat in a fat-rich meal can make it down to the colon. This may result in “detrimental changes” in our gut microbiome, as well as weight gain, increased leaky gut, and pro-inflammatory changes. For example, there may be a drop in beneficial Bifidobacteria and a decrease in overall short-chain fatty acid production, both of which would be expected to increase the risk of gastrointestinal disorders. 
     
    Striking at the heart of the matter, what might all of that saturated fat be doing to our heart? If you look at low-carbohydrate diets and all-cause mortality, those who eat lower-carb diets suffer “a significantly higher risk of all-cause mortality,” meaning they live, on average, significantly shorter lives. However, from a heart-disease perspective, it matters if it’s animal fat or plant fat. Based on the famous Harvard cohorts, eating more of an animal-based, low-carb diet was associated with higher death rates from cardiovascular disease and a 50 percent higher risk of dying from a heart attack or stroke, but no such association was found for lower-carb diets based on plant sources.  
     
    And it wasn’t just Harvard. Other researchers have also found that “low-carbohydrate dietary patterns favoring animal-derived protein and fat sources, from sources such as lamb, beef, pork, and chicken, were associated with higher mortality, whereas those that favored plant-derived protein and fat intake, from sources such as vegetables, nuts, peanut butter, and whole-grain bread, were associated with lower mortality…” 
     
    Cholesterol production in the body is directly correlated to body weight, as you can see in the graph below and at 3:50 in my video. 

    Every pound of weight loss by nearly any means is associated with about a one-point drop in cholesterol levels in the blood. But if we put people on very-low-carb ketogenic diets, the beneficial effect on LDL bad cholesterol is blunted or even completely neutralized. Counterbalancing changes in LDL or HDL (what we used to think of as good cholesterol) are not considered sufficient to offset this risk. You don’t have to wait until cholesterol builds up in your arteries to have adverse effects either; within three hours of eating a meal high in saturated fat, you can see a significant impairment of artery function. Even with a dozen pounds of weight loss, artery function worsens on a ketogenic diet instead of getting better, which appears to be the case with low-carb diets in general.  

    For more on keto diets, check out my video series here. 

    And, to learn more about your microbiome, see the related videos below.

    Michael Greger M.D. FACLM

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  • Can You Sustain Weight Loss on Ketosis?  | NutritionFacts.org

    Can You Sustain Weight Loss on Ketosis?  | NutritionFacts.org

    Might the appetite-suppressing effects of ketosis improve dietary compliance? 

    The new data are said to debunk “some, if not all, of the popular claims made for extreme carbohydrate restriction,” but what about ketones suppressing hunger? In a tightly controlled metabolic ward study where the ketogenic diet made things worse, everyone ate the same number of calories, but those on a keto diet lost less body fat. But, out in the real world, all of those ketones might spoil your appetite enough that you’d end up eating significantly less overall. On a low-carb diet, people end up storing 300 more calories of fat every day. Outside of the laboratory, though, if you were in a state of ketosis, might you be able to offset that if you were able to sustainably eat significantly less? 
     
    Paradoxically, as I discuss in my video Is Weight Loss on Ketosis Sustainable?, people may experience less hunger on a total fast compared to an extremely low-calorie diet. This may be thanks to ketones. In this state of ketosis, when you have high levels of ketones in your bloodstream, your hunger is dampened. How do we know it’s the ketones? If you inject ketones straight into people’s veins, even those who are not fasting lose their appetite, sometimes even to the point of getting nauseated and vomiting. So, ketones can explain why you might feel hungrier after a few days on a low-calorie diet than on a total zero-calorie diet—that is, a fast. 
     
    Can we then exploit the appetite-suppressing effects of ketosis by eating a ketogenic diet? If you ate so few carbs to sustain brain function, couldn’t you trick your body into thinking you’re fasting and get your liver to start pumping out ketones? Yes, but is it safe? Is it effective? 
     
    As you can see below and at 1:58 in my video, a meta-analysis of 48 randomized trials of various branded diets found that those advised to eat low-carb diets and those told to eat low-fat ones lost nearly identical amounts of weight after a year.

    Obviously, high attrition rates and poor dietary adherence complicate comparisons of efficacy. The study participants weren’t actually put on those diets; they were just told to eat in those ways. Nevertheless, you can see how even just moving in each respective direction can get rid of a lot of CRAP (which is Jeff Novick’s acronym for Calorie-Rich And Processed foods). After all, as you can see in the graph below and at 2:37 in my video, the four largest calorie contributors in the American diet are refined grains, added fats, meat, and added sugars. 

    Low-carb diets cut down on refined grains and added sugars, and low-fat diets tend to cut down on added fats and meat, so they both tell people to cut down on donuts. Any diet that does that already has a leg up. I figure a don’t-eat-anything-that-starts-with-the-letter-D diet could also successfully cause weight loss if it caused people to cut down on donuts, danishes, and Doritos, even if it makes no nutritional sense to exclude something like dill. 

    The secret to long-term weight-loss success on any diet is compliance. Diet adherence is difficult, though, because any time you try to cut calories, your body ramps up your appetite to try to compensate. This is why traditional weight-loss approaches, like portion control, tend to fail. For long-term success, measured not in weeks or months but in years and decades, this day-to-day hunger problem must be overcome. On a wholesome plant-based diet, this can be accomplished thanks in part to calorie density because you’re just eating so much food. On a ketogenic diet, it may be accomplished with ketosis. In a systematic review and meta-analysis entitled “Do Ketogenic Diets Really Suppress Appetite,” researchers found that the answer was yes. Ketogenic diets also offer the unique advantage of being able to track dietary compliance in real-time with ketone test strips you can pee on to see if you’re still in ketosis. There’s no pee stick that will tell you if you’re eating enough fruits and veggies. All you have is the bathroom scale. 

    Keto compliance may be more in theory than practice, though. Even in studies where ketogenic diets are being used to control seizures, dietary compliance may drop below 50 percent after a few months. This can be tragic for those with intractable epilepsy, but for everyone else, the difficulty in sticking long-term to ketogenic diets may actually be a lifesaver. I’ll talk about keto diet safety next. 

    The keto diet is in contrast to a diet that would actually be healthful to stick to. See, for example, my video series on the CHIP program here. 
     
    This was the fourth video in a seven-part series on keto diets. If you haven’t yet, be sure to watch the others listed in the related videos below. 

    Michael Greger M.D. FACLM

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  • Can You Lose Weight on a Keto Diet?  | NutritionFacts.org

    Can You Lose Weight on a Keto Diet?  | NutritionFacts.org

    Let’s dive into ketogenic diets and their $33-billion gimmick. 

    The carbohydrate–insulin model of obesity, the underlying theory that ketogenic diets have some sort of metabolic advantage, has been experimentally falsified. Keto diet proponents’ own studies showed the exact opposite: Ketogenic diets actually put you at a metabolic disadvantage and slow the loss of body fat. How much does fat loss slow down on a low-carb diet?  

    As I discuss in my video Keto Diet Results for Weight Loss, if you cut about 800 calories of carbohydrates from your diet a day, you lose 53 grams of body fat a day. But if you cut the same number of fat calories, you lose 89 grams of fat a day. Same number of calories cut, but nine butter pats’ worth of extra fat melting off your body each day on a low-fat diet, compared to a low-carb one. Same number of calories, but about 80 percent more fat loss when you cut down on fat instead of carbs. You can see a graph of these results below and at 1:07 in my video. The title of the study speaks for itself: “Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss Than Carbohydrate Restriction in People with Obesity.” 

    Just looking at the bathroom scale, though, would mislead you into thinking the opposite. After six days on the low-carb diet, study subjects lost four pounds. On the low-fat diet, they lost less than three pounds, as you can see in the graph below and at 1:40 in my video. So, according to the scale, it looked like the low-carb diet wins hands down. You can see why low-carb diets are so popular. What was happening inside their bodies, however, tells the real story. The low-carb group was losing mostly lean mass—water and protein. This loss of water weight helps explain why low-carb diets have “been such a persistent theme for authors of diet books and such ‘cash cows’ for publishers,” going back more than the last 150 years. That’s their secret. As one weight-loss expert noted, “Rapid water loss is the $33-billion diet gimmick.” 

    When you eat carbohydrates, your body bulks up your muscles with glycogen for quick energy. Eat a high-carbohydrate diet for three days, and you may add about three pounds of muscle mass onto your arms and legs, as you can see below and at 2:34 in my video. Those glycogen stores drain away on a low-carb diet and pull water out with it. (The ketones also need to be flushed out of the kidneys, pulling out even more water.) On the scale, that can manifest as four more pounds coming off within ten days, but that “was all accounted for by losses in total body water”—that is water loss. 

    The bottom line: Keto diets just don’t hold water. 

    The thrill of seeing the pounds come off so quickly on the scale keeps many coming back to the low-carb altar. When the diet fails, the dieters often blame themselves, but the intoxication of that initial, rapid weight loss may tempt them back, like getting drunk again after forgetting how terrible the last hangover was. This has been dubbed the “false hope syndrome.” “The diet industry thrives for two reasons—big promises and repeat customers,” something low-carb diets were built for, given that initial, rapid water loss. 

    What we care about is body fat. In six days, the low-fat diet extracted a total of 80 percent more fat from the body than the low-carb diet. It’s not just one study either. As you can see below and at 3:54 in my video, you can look at all of the controlled feeding trials where researchers compared low-carb diets to low-fat ones, swapping the same number of carb calories for fat calories or vice versa. If a calorie is just a calorie, then all of the studies should have crossed that zero line in the middle, straddling “favors low-fat diet” and “favors low-carb diet,” and indeed six did. One study showed more fat loss on a low-carb diet, but every other study favored the low-fat diet—more loss of body fat eating the same number of calories. When you put all of the studies together, we’re talking 16 more grams of daily body fat lost on the low-fat diets. That’s like four more pats of butter melting off your body on a daily basis. Less fat in the mouth means less fat on the hips, even when you’re taking in the same number of calories. 

    This is the third installment of my seven-part series on keto diets. 

    This keto research came from the deep dive I took for my book How Not to Diet. (All proceeds I receive from my books are donated to charity.) You can learn more about How Not to Diet and order it here. Also please feel free to check out some of my popular weight-loss videos in related videos below. 

    Michael Greger M.D. FACLM

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  • Testing the Keto Diet Theory  | NutritionFacts.org

    Testing the Keto Diet Theory  | NutritionFacts.org

    Do low-carb and ketogenic diets have a metabolic advantage for weight loss? 

    When you don’t eat enough carbohydrates, you force your body to burn more fat. “However, this rise in fat oxidation [burning] is often misconstrued as a greater rate of net FM [fat-mass] reduction” in the body, ignoring the fact that, on a ketogenic diet, your fat intake shoots up, too. What happens to your overall body fat balance? You can’t empty a tub by widening the drain if you’re opening the faucet at the same time. Low-carb advocates had a theory, though, the “carbohydrate–insulin model of obesity,” which I discuss in my video Keto Diet Theory Put to the Test.  

    Proponents of low-carb diets, whether a ketogenic diet or a more relaxed form of carbohydrate restriction, suggested that decreased insulin secretion would lead to less fat storage, so even if you were eating more fat, less of it would stick to your frame. We’d burn more and store less, the perfect combination for fat loss—or so the theory went. To their credit, instead of just speculating about it, they decided to put it to the test. 

    Gary Taubes formed the Nutrition Science Initiative (NuSI) to sponsor research to validate the carbohydrate–insulin model. He’s the journalist who wrote the controversial 2002 New York Times Magazine article “What If It’s All Been a Big Fat Lie?” which attempted to turn nutrition dogma on its head by arguing in favor of the Atkins diet with its bunless bacon cheeseburgers based on the carbohydrate–insulin model. (Much of Nina Teicholz’s book The Big Fat Surprise is simply recycled from Taubes’ earlier work.)  

    In response, some of the very researchers Taubes cited to support his thesis accused him of twisting their words. One said, “The article was incredibly misleading…I was horrified.” Said another, “He took this weird little idea and blew it up, and people believed him…What a disaster.” It doesn’t matter what people say, though. All that matters is the science. 

    Taubes attracted $40 million in committed funding for his Nutrition Science Initiative to prove to the world that you could lose more body fat on a ketogenic diet. NuSI contracted noted researcher Kevin Hall from the National Institutes of Health to perform the study. Seventeen overweight or obese men were effectively locked in what’s called a metabolic ward for two months to allow researchers total control over their diets. For the first month, they were placed on a typical high-carbohydrate diet (50 percent carbs, 35 percent fat, 15 percent protein), then were switched to a low-carb ketogenic diet (only 5 percent of calories from carbohydrates and 80 percent fat) for the second month. Both diets had the same number of daily calories. So, if a calorie is a calorie when it comes to weight loss, there should be no difference in body fat loss on the regular diet versus the ketogenic diet. If Taubes was right, though, if fat calories were somehow less fattening, then body fat loss would become accelerated on a keto diet. Instead, in the very study funded by the Nutrition Science Initiative, researchers found that body fat loss slowed during the ketogenic diet. 

    Why do people think the keto diet works if it actually slows fat loss? Well, as you can see in the graph below and at 3:40 in my video, if you looked only at the readings on bathroom scales, the ketogenic diet would seem like a smashing success. Participants went from losing less than a pound a week on the regular diet during the first two weeks of the study to losing three and a half pounds within seven days after switching to the ketogenic diet. What was happening inside their bodies, however, told a totally different story: Their rate of body fat loss was slowed by more than half. So, most of what they were losing was just water weight. It’s presumed the reason they started burning less fat on a ketogenic diet was because, without the preferred fuel of carbohydrates, their bodies started burning more of their own protein—and that’s exactly what happened. Switching to a ketogenic diet made them lose less fat mass and more fat-free mass. Indeed, they lost more lean mass. That may help explain why the leg muscles of CrossFit trainees placed on a ketogenic diet may shrink as much as 8 percent. The vast lateralis, the biggest quad muscle in your leg, shrunk in thickness by 8 percent on a ketogenic diet. 

    Yes, the study subjects started burning more fat on the ketogenic diet, but they were also eating so much more fat on the keto diet that they ended up retaining more fat in their body, despite the lower insulin levels. This is “diametrically opposite” to what the keto crowd predicted, and this is from the guy Nutrition Science Initiative paid to support its theory. In science-speak, “the carbohydrate–insulin model failed experimental interrogation.” 

    In light of this “experimental falsification” of the low-carb theory, the Nutrition Science Initiative effectively collapsed but, based on its tax returns, not before Taubes and his co-founder personally pocketed millions of dollars in compensation. 

    This is the second installment in my seven-part series on keto diets. In case you missed them, check out the other related videos below.  

    The more things change, the more they stay the same. I created a whole website about the Atkins Diet, but, sadly, people keep falling into the low-carb trap. You can find some of my older videos on low-carb diets listed below. 

    Michael Greger M.D. FACLM

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  • Does Chewing Gum Burn Calories? | NutritionFacts.org

    Does Chewing Gum Burn Calories? | NutritionFacts.org

    What are the effects of chewing gum on hunger and appetite?  

    “Horace Fletcher,” proclaimed one of his obituaries in 1919, “taught the world to chew.” Also known as the “Great Masticator,” Fletcher was a health reformer who popularized the idea of chewing each mouthful more than 32 times—“once for every tooth.” It wasn’t put to the test, though, until nearly a century later. In that study, participants were told to eat pasta until they felt “comfortably full” and were randomized to chew each mouthful either 10 times or 35 times before swallowing. The subjects were told the study was about the effects of chewing on mood, but that was just a ruse. The researchers really wanted to know whether prolonged chewing reduced food intake. And, as it turned out, those who chewed more felt full earlier than those who chewed less, such that they ended up eating about a third of a cup less pasta overall. 

    If chewing suppresses the appetite in some way, what about chewing gum as a weight-loss strategy? As I discuss in my video How Many Calories Do You Burn Chewing Gum?, an article entitled “Benefits of Chewing Gum” suggested as much by saying that it “may be a useful behavior modification tool in appetite control and weight management,” but it was co-written by the executive director of The Wrigley Science Institute and a senior manager at the Wm Wrigley Jr Company. Why don’t we see what the unbiased science says? 

    Big Gum likes to point to a letter published in 1999 in The New England Journal of Medicine. In it, Mayo Clinic researchers claimed that chewing gum could burn 11 calories an hour. Critics pointed to the fact that they didn’t really test “typical” gum chewing; they instead tested chewing the equivalent of four sticks of gum “at a very rapid cadence.” Specifically, the participants were told to chew at a frequency of exactly 100 Hertz (Hz) “with the aid of a metronome” for 12 minutes. That seemed to burn 2.2 calories, hence, potentially 11 calories an hour. 

    One might have had more confidence in the Mayo scientists’ conclusion had they not lacked a fundamental understanding of basic units. As defined by Merriam-Webster, hertz is a unit of frequency equal to one cycle per second, so 100 Hz would mean 100 chews per second. (That would be a very rapid cadence!) If it’s true that 11 calories may be burned an hour, though, that means you could burn more calories actively chewing gum while sitting in a chair than you would if you weren’t chewing gum while upright at a standing desk. 

    In fact, as you can see in the graph below and at 2:24 in my video, chewing one small piece of gum at your own pace may only burn about three calories an hour, which would approximate the calorie content of the sugar-free gum itself. However, chewing off the calories of a piece of sugar-sweetened gum might take all day. What about the purported appetite-suppressing effect of all that chewing, though? 

    The results from studies on the effects of chewing gum on hunger are all over the place. For example, as you can see in the graph below and at 2:50 in my video, one showed decreased appetite, another showed no effect, and yet another even showed significantly increased hunger in women after chewing gum. The more important question, though, is whether there are any changes in subsequent calorie intake. Again, the findings are mixed. 

    One study, as you can see in the graph below and at 3:12 in my video, even found that while chewing gum didn’t impact M&M consumption much, it did appear to decrease the consumption of healthy snacks. Interesting, but the researchers used mint gum, and the healthy snacks included mandarin orange slices. So, that may have just been an orange juice-after-tooth-brushing effect.  

    It can take an hour before the residual taste effect of mint toothpaste dissipates. This is bad if it cuts your fruit intake, but what about harnessing this power against Pringles? An international group of researchers had people eat Pringles potato chips for 12 minutes, interrupting them every 3 minutes to swish with a menthol mouthwash. As you can see in the graph below and at 3:50 in my video, compared to those in the control groups (swishing with water or nothing at all), the minty mouthwash group cut their consumption by 29 percent. The researchers concluded: “If a consumer finds themselves snacking on too many crisps [potato chips] during a given eating occasion, one potential strategy could be intervening by having a peppermint tea, menthol flavoured chewing gum, or brushing their teeth, to slow down or stop snacking.” 

    What we’re wondering about, though, is weight loss. Even if a little tweak like chewing gum can affect the consumption of a single snack, your body could just compensate by eating more later in the day. The only way to know for sure if chewing gum can be used as a weight-loss hack is to put it to the test, which I cover in my video Does Chewing Gum Help with Weight Loss? 

    For more information on calories and weight loss, check out related videos below. 

    Michael Greger M.D. FACLM

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  • Chewing Gum for Weight Loss?  | NutritionFacts.org

    Chewing Gum for Weight Loss?  | NutritionFacts.org

    If extra chewing is effective in suppressing your appetite when it comes to food, what about chewing gum as a weight-loss strategy? 

    As I discuss in my video Does Chewing Gum Help with Weight Loss?, chewing gum may only burn about three calories an hour, but the calorie expenditure isn’t only working your little jaw muscles. For some reason, chewing gum revs up your heart rate as much as 12 extra beats per minute after chewing two sticks of gum, even if you’re just sitting quietly, as you can see in the graph below and at 0:21 in my video. It also works while walking, increasing your heart rate by about three more beats per minute (and proving scientifically that people can indeed walk and chew gum at the same time).  

    Does this translate into weight loss? Researchers at the University of Buffalo asked study participants to either chew gum before every single eating occasion or not chew any gum at all for a number of weeks. On the gum-chewing weeks, the subjects didn’t just have to chew gum before each meal, but also before each snack or drink that contained any calories. That may have been too much, so the participants actually ended up eating on fewer occasions, switching from four meals a day on average down closer to three. They ended up eating more calories at each of those fewer meals, though, and had no overall significant change in caloric intake and, no surprise, had no change in weight. See the charts below and at 1:08 in my video. 

    University of Alabama researchers tried a different tack, randomizing people to chew gum after and between meals. After two months, compared to those randomized to avoid gum entirely, no improvements were noted in weight, body mass index (BMI), or waist circumference. However, some studies have suggested that chewing gum has an appetite-suppressing effect. For example, as you can see below and at 1:51 in my video, in one study, people ate 68 fewer calories of pasta at lunch after 20 minutes of chewing gum, but other studies have shown differently. 

    Whenever there are conflicting findings, instead of just throwing up our hands, it can be useful to try to tease out any study differences that could potentially account for the disparate results. The obvious consideration is the funding source. That failed University of Alabama weight-loss study was funded by a gum company, so the outcomes are not necessarily predetermined. 

    As well, different types of gum using different sweeteners may have contributed to the diversity of findings. As you can see in the graphs below and at 2:35 in my video, a study that found that chewing gum may actually increase appetite was done with aspartame-sweetened gum. People reported feeling hungrier after chewing the sweetened gum—and not only compared to no gum, but compared to chewing the same gum with no added aspartame. It’s true that not one randomized controlled trial has ever shown a benefit to “chewing gum as a strategy for weight loss,” but they all used gum containing artificial sweeteners.

    There was a landmark study that showed that the size of a sip matters when it comes to reducing the intake of sweet beverages. When study participants took one sip every two seconds or a quadruple-sized gulp every eight seconds, but with the same ingestion rate of 150 grams per minute, the smaller sip group won out, satiating after about one-and-a-half cups compared to two cups when taking larger gulps, as you can see in the graph below and at 3:13 in my video. This is thought to be because of increased oro-sensory exposure, so our brain picks up the more frequent pulses of flavor and calories. But repeat the experiment with an artificially sweetened diet drink, and the effect appears to be blunted, as you can see in the graph below and at 3:38 in my video. So, might a different type of gum have a different effect? The positive pasta study I discussed earlier was performed using gum sweetened mainly with sorbitol, a sweet compound that’s found naturally in foods like prunes, and, like prunes, can have a laxative effect.

    Case reports like “An Air Stewardess with Puzzling Diarrhea” unveil what can happen when you have 60 sticks of sorbitol-sweetened sugar-free gum a day. Another report was entitled “Severe Weight Loss Caused by Chewing Gum.” A 21-year-old woman ended up malnourished after suffering up to a dozen bouts of diarrhea a day for eight months due to the 30 grams of sorbitol she was getting chewing sugar-free gum and candies every day. Most people suffer gas and bloating at 10 daily grams of sorbitol, which is about eight sticks of sorbitol-sweetened gum, and, at 20 grams, most get cramps and diarrhea. So, you want to be careful how much you get. 

    The bottom line is that we have no good science showing that chewing gum results in weight loss. Could that be because the studies used artificial sweeteners that “may have counteracted” any benefits? Maybe, but the most obvious explanation for the results to date “is that chewing gum simply is not an efficacious weight-loss strategy”—and that’s coming from researchers funded by the gum company itself. 

    How Many Calories Do You Burn Chewing Gum? Watch the video to find out. For information on both artificial and natural low-calorie sweeteners, check out the related videos below.

    Michael Greger M.D. FACLM

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  • Cutting Calories Could Slow the Pace of Aging: Study

    Cutting Calories Could Slow the Pace of Aging: Study

    Feb. 14, 2023 – A new study says we can slow the pace at which we age by 2% to 3% if we lower the number of calories we eat by 25%. That may seem like a little benefit for a large cut in calories. But experts say it’s actually a pretty big deal. 

    “In other studies, that same difference in pace of aging had meaningful consequences for people’s risk of dying,” says senior study author Daniel W. Belsky, PhD, a researcher at the Butler Columbia Aging Center at Columbia University Mailman School of Public Health in New York City.

    Cutting calories by 25% slowed down the pace of aging in young and middle-aged adults by a few percentage points, compared to people who continued eating normally, the new research reveals. This first-of-its-kind study in humans adds to evidence from animal studies that the rate of aging can be changed. 

    Compared to 75 people who ate normally, the 145 people randomly assigned to cut back their calories slowed their pace of aging by 2% to 3% over 2 years in the  randomized controlled trial. 

    For example, a similar slowdown in the pace of aging was associated with a 10% to 15% lower risk of dying over 10 to 15 years in previous work, Belsky says. “So 2 to 3% slower aging doesn’t sound like maybe that big of a deal – but 10 to 15 percent reduction in risk of dying seems like a big deal.” 

    Results of the study were published last week in the journal Nature Aging. 

    Even though the pace of aging slowed, the researchers did not find significant changes on two biological aging measures in the study, suggesting more work is needed. 

    The findings “are intriguing in that caloric restriction seemed to show a slower pace of aging in healthy adults,” says Vandana Sheth, a registered dietitian nutritionist and owner of a nutrition consulting firm in Los Angeles. “This can have a significant impact on population health. However, larger studies need to be done to follow up on these findings.”

    ‘Exciting Result’

    Asked if the findings imply aging could be slowed down in people, Belsky said, “That is the … exciting result from the trial. These results suggest it may be possible to slow the pace of biological aging with a behavioral intervention.”

    But not everyone is completely convinced. 

    “This is good suggestive evidence that caloric restriction can modify aspects of biological aging in humans, similar to what has been known in laboratory animals for many decades,” says Matt Kaeberlein, PhD, director of the Healthy Aging and Longevity Research Institute at the University of Washington in Seattle and senior author of “Antiaging diets: Separating fact from fiction,” a 2021 review article in Science. 

    Part of his concern is that cutting your calories by a quarter may not be a sustainable long-term strategy.  

    “It’s important to keep in mind that these measurements only report on a portion of biological aging and are probably not an accurate overall measurement of biological age or the rate of biological aging,” Kaeberlein says. The findings might suggest that “at the population level, a 25% reduction in caloric intake is unlikely to have large effects on biological aging unless implemented over many years, which is likely not reasonable for most people.”

    Insight Into Intermittent Fasting?

    Cutting back on calories is related to other dietary strategies, including intermittent fasting and time-restricted eating, Belsky says. “Intermittent fasting and time-restricted eating are nutritional interventions that have been developed, in part, because in experiments with animals, they have some of the same biological effects as calorie restriction.”

    There remain many unanswered questions. 

    “There are people who would argue that the reason calorie restriction does what it does is because when people are calorie-restricted, they also tend to restrict the times when they eat,” Belsky says. “They tend to have these longer fasts during the day.” 

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