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Tag: weight gain

  • What Is the Role of Our Genes in the Obesity Epidemic?  | NutritionFacts.org

    What Is the Role of Our Genes in the Obesity Epidemic?  | NutritionFacts.org

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    The “fat gene” accounts for less than 1 percent of the differences in size between people.

    To date, about a hundred genetic markers have been linked to obesity, but when you put them all together, overall, they account for less than 3 percent of the difference in body mass index (BMI) between people. You may have heard about the “fat gene,” called FTO, short for FaT mass and Obesity-associated). It’s the gene most strongly linked to obesity, but it explains less than 1 percent of the difference in BMI between people, a mere 0.34 percent. 

    As I discuss in my video The Role of Genes in the Obesity Epidemic, FTO codes for a brain protein that appears to affect our appetite. Are you one of the billion people who carry the FTO susceptibility genes? It doesn’t matter because it only appears to result in a difference in intake of a few hundred extra calories a year. The energy imbalance that led to the obesity epidemic is on the order of hundreds of calories a day, and that’s the gene known so far to have the most effect. The chances of accurately predicting obesity risk based on FTO status is “only slightly better than tossing a coin.” In other words, no, those genes don’t make you look fat.

    When it comes to obesity, the power of our genes is nothing compared to the power of our fork. Even the small influence the FTO gene does have appears to be weaker among those who are physically active and may be abolished completely in those eating healthier diets. FTO only appears to affect those eating diets higher in saturated fat, which is predominantly found in meat, dairy, and junk food. Those eating more healthfully appear to be at no greater risk of weight gain, even if they inherited the “fat gene” from both of their parents.

    Physiologically, FTO gene status does not appear to affect our ability to lose weight. Psychologically, knowing we’re at increased genetic risk for obesity may motivate some people to eat and live more healthfully, but it may cause others to fatalistically throw their hands up in the air and resign themselves to thinking that it just runs in their family, as you can see in the graph below and at 2:11 in my video. Obesity does tend to run in families, but so do lousy diets. 

    Comparing the weight of biological versus adopted children can help tease out the contributions of lifestyles versus genetics. Children growing up with two overweight biological parents were found to be 27 percent more likely to be overweight themselves, whereas adopted children placed in a home with two overweight parents were 21 percent more likely to be overweight. So, genetics do play a role, but this suggests that it’s more the children’s environment than their DNA.

    One of the most dramatic examples of the power of diet over DNA comes from the Pima Indians of Arizona. As you can see in the graph below and at 3:05 in my video, they not only have among the highest rates of obesity, but they also have the highest rates of diabetes in the world. This has been ascribed to their relatively fuel-efficient genetic makeup. Their propensity to store calories may have served them well in times of scarcity when they were living off of corn, beans, and squash, but when the area became “settled,” their source of water, the Gila River, was diverted upstream. Those who survived the ensuing famine had to abandon their traditional diet to live off of government food programs and chronic disease rates skyrocketed. Same genes, but different diet, different result. 

    In fact, a natural experiment was set up. The Pima living over the border in Mexico come from the same genetic pool but were able to maintain more of their traditional lifestyle, sticking with their main staples of beans, wheat flour tortillas, and potatoes. Same genes, but seven times less obesity and about four times less diabetes. You can see those graphs below and at 3:58 and 4:02 in my video. Genes may load the gun, but diet pulls the trigger.

    Of course, it’s not our genes! Our genes didn’t suddenly change 40 years ago. At the same time, though, in a certain sense, it could be thought of as all in our genes. That’s the topic of my next video The Thrifty Gene Theory: Survival of the Fattest.

    This is the second in an 11-video series on the obesity epidemic. If you missed the first one, check out The Role of Diet vs. Exercise in the Obesity Epidemic. 

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    Michael Greger M.D. FACLM

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  • The Roles Diet and Exercise Play in the Obesity Epidemic  | NutritionFacts.org

    The Roles Diet and Exercise Play in the Obesity Epidemic  | NutritionFacts.org

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    The common explanations for the cause of the obesity epidemic put forward by the food industry and policymakers, such as inactivity or a lack of willpower, are not only wrong, but actively harmful fallacies.

    Obesity isn’t new, but the obesity epidemic is. We went from a few corpulent kings and queens, like Henry VIII or Louis VI (known as Louis le Gros, or “Louis the Fat”), to a pandemic of obesity, now considered to be “arguably the gravest and most poorly controlled public health threat of our time.” As you can see below and at 0:34 in my video The Role of Diet vs. Exercise in the Obesity Epidemic, about 37 percent of American men are obese and 41 percent of American women, with no end in sight. Earlier reports had suggested that the rise in obesity was at least slowing down, but even that doesn’t appear to be the case. Similarly, we had thought we were turning the corner on childhood obesity “[a]fter 35 years of unremittingly bad news,” but the bad news continues. Childhood and adolescent obesity rates have continued to rise, now into the fourth decade. 

    Over the last century, obesity appears to have jumped ten-fold, from about 1 in 30 to now 1 in 3, but it wasn’t a steady rise. As you can see in the graph below and at 1:15 in my video, something seems to have happened around the late 1970s—and not just in the United States, but around the globe. The obesity pandemic took off at about the same time in the 1970s and 1980s in most high-income countries. The fact that the rapid rise “seemed to begin almost concurrently” across the industrialized world suggests a common cause. What might that trigger have been? 

    Any potential driver would have to be global and “coincide with the upswing of the epidemic.” So, the change would have had to have started about 40 years ago and would have had to have been able to spread rapidly around the globe. Let’s see how all the various theories stack up. For example, as you can see below and at 1:55 in my video, some have blamed changes in our built environment and shifts in city planning that have made our communities less conducive to walking, biking, and grocery shopping. That doesn’t meet our criteria for a credible cause, though, because there was no universal, simultaneous change in our neighborhoods within that time frame.

    When researchers surveyed hundreds of policymakers, most blamed the obesity epidemic on a “lack of personal motivation.” Do you see how little sense that makes? In the United States, for example, obesity shot up across the entire population in the late 1970s, as you can see at 2:26 in my video. I concur with the researchers who “believe it is implausible that each age, sex, and ethnic group, with massive differences in life experience and attitudes, had a simultaneous decline in willpower related to healthy nutrition or exercise.” More plausible than a global change like our characters would be some global change like our lives. 

    The food industry blames inactivity. “If all consumers exercised,” said the CEO of PepsiCo, “obesity wouldn’t exist.” Coca-Cola went a step further, spending $1.5 million to create the Global Energy Balance Network to downplay the role of diet. Leaked emails show the company planned on using the front to “serve as a ‘weapon’ to ‘change the conversation’ about obesity in its ‘war’ with public health.

    This tactic is so common among food and beverage companies that it even has a name: “leanwashing.” You’ve heard of greenwashing, where companies deceptively pretend to be environmentally friendly. Leanwashing is the term used to describe companies that try to position themselves as helping to solve the obesity crisis when they’re instead directly contributing to it. For example, the largest food company in the world, Nestlé, has “rebranded itself as the ‘world’s leading nutrition, health and wellness company.” Yes, that Nestlé, makers of Nesquik, Cookie Crisp, and historically more than a hundred different brands of candy, including Butterfinger, Kit Kat, Goobers, Gobstoppers, Runts, and Nerds. Another one of its slogans is “Good Food, Good Life.” Its Raisinets may have some fruit, but Nestlé seems to me more Willy Wonka than wellness. 

    The constant corporate drumbeat of overemphasis on physical inactivity appears to be working. In response to the Harris poll question, “Which of these do you think are the major reasons why obesity has increased?,” a “huge majority of 83% chose lack of exercise, while only 34% chose excessive calorie consumption.” “Confusion about the effect of exercise on the energy balance” has been identified as one of the most common misconceptions about obesity. The scientific community has “come to a fairly decisive conclusion” that the factors governing calorie intake more powerfully affect overall calorie balance. It’s our fast food more than our slow motion. 

    “There is considerable debate in the literature today about whether physical activity has any role whatsoever in the epidemic of obesity that has swept the globe since the 1980s.” The increase in caloric intake per person is more than enough to explain the obesity epidemic in the United States and also explain it globally. If anything, the level of physical activity over the last few decades has gone up slightly in both Europe and North America. Ironically, this may be a result of the extra energy it takes to move around our heavier bodies, making it a consequence of the obesity problem rather than the cause.

    “Formal exercise plays a very small role in the total daily physical activity energy expenditure.” Think how much more physical work people used to do in the workplace, on the farm, or even in the home. It’s not just the shift in collar color from blue to white. Increasing automation, computerization, mechanization, motorization, and urbanization have all contributed to increasingly more sedentary lifestyles over the last century—and that’s the problem with the theory. The occupational shifts and advent of labor-saving devices “have been gradual and largely predated the dramatic increase in weight gain across the developed world in the past few decades.” Washing machines, vacuum cleaners, and the Model T were all invented before 1910. Indeed, when put to the test using state-of-the-art methods to measure energy in and energy out, it was caloric intake, not physical activity, that predicted weight gain over time. 

    The common misconception that obesity is mostly due to lack of exercise may not just be a benign fallacy. Personal theories of causation appear to impact people’s weight. Those who blame insufficient exercise are significantly more likely to be overweight than those who implicate a poor diet. Put those who believe lack of exercise causes obesity in a room with chocolate, and they can covertly be observed consuming more candy. Those holding that view may be different in other ways, though. You can’t prove cause and effect until you put it to the test. And, indeed, as you can see in the graph below, and at 7:22 in my video, people randomized to read an article implicating inactivity went on to eat significantly more sweets than those reading about research that indicated diet. A similar study found that those presented with research blaming genetics subsequently ate significantly more cookies. The title of that paper? “An Unintended Way in Which the Fat Gene Might Make You Fat.” 

    When I sat down to write How Not to Diet, I knew this “what triggered the obesity epidemic” was going to be a big question I had to face. Was it inactivity (just kids sitting around playing video games or scrolling on their phones)? Was it genetic? Was it epigenetic (something turning on our fat genes)? Or was it just the food? Were we eating more fat all of a sudden? More carbs? More processed foods? Or were we just eating more period, because of bigger serving sizes or more snacking? Inquiring minds wanted to know. 

    This is the first in an 11-video series to answer this question, which I originally released in a two-hour webinar in 2020. Check out the webinar digital download here. Or, check them out in the related posts below.  

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    Michael Greger M.D. FACLM

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  • Does Marijuana Affect Weight Gain or Bone Density?  | NutritionFacts.org

    Does Marijuana Affect Weight Gain or Bone Density?  | NutritionFacts.org

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    Are the apparent adverse effects of heavy cannabis use on the bone just due to users being thinner? 

    It’s been recognized for decades that cigarette smoking can have “a major effect” on bone health, “increasing the lifetime risk of hip fracture by about half.” It also appears to impair bone healing, so much so that surgeons ask if they should discriminate against smokers because their bone and wound-healing complication rates are so high. What about smoking marijuana?

    As I discuss in my video Effects of Marijuana on Weight Gain and Bone Density, “There is accumulating evidence to suggest that cannabinoids [cannabis compounds] and their receptors play important roles in bone metabolism by regulating bone mass, bone loss, and bone cell function.” Okay, but are they “friend or foe?” 

    “Results from research on cannabinoids and bone mineral density in rodent models have been inconsistent. Some studies show increased bone formation, others have demonstrated accelerated bone loss, and yet others have shown no association. This variation in results may be due [in part] to differences in the mouse strain, sex, age…” If you can’t even extrapolate from one mouse to another, how can you extrapolate from mice to human beings?

    What if you just measure cannabis use and bone mineral density in people? Researchers tested thousands of adults and asked them about their cannabis use. There did not appear to be any link between the two, which is a relief. However, in this study, “heavy” cannabis use was defined as just five or more days of use in the previous 30 days. The researchers didn’t ask beyond that, so, theoretically, someone who smoked just five joints in their entire life could be categorized as a “heavy user” if they happened to use it five times in the last four weeks.

    How about cannabis use on 5,000 separate occasions over a lifetime? Now that’s a heavy user—decades of regular use. In that case, heavy use was “associated with low bone mineral density and an increased risk of fractures”—about double the fracture rate presumably due to lower bone density in the hip and spine, although heavy cannabis users were also thinner on average, and thinner people have lighter bones.

    Hip fracture risk goes down as our weight goes up. Nearly half of underweight women have osteoporosis, but less than 1 percent of obese women do, which makes total sense. Being obese forces our body to make our bones stronger to carry around all of that extra weight. That’s why weight-bearing exercise is so important to constantly put stress on our skeleton. When it comes to our bones, it’s use it or lose it. That’s why astronauts can lose a percent of their bone mass every month in “long-duration spaceflight.” Their bodies aren’t stupid. Why waste all that energy making a strong skeleton if you aren’t going to put any weight on it? 

    So, maybe the reason heavy cannabis users have frailer bones is because they tend to be about 15 pounds lighter. Wait a second. Marijuana users are slimmer? What about the munchies? “The lower BMI that was observed in heavy cannabis users at first sight seems counterintuitive,” given marijuana’s appetite stimulation, but this isn’t the first time this has been noted. 

    “Popular culture commonly depicts marijuana users as a sluggish, lethargic, and unproductive subculture of compulsive snackers,” and marijuana has indeed been found to increase food intake. A single hit can increase appetite, so you’d expect obesity rates to rise in states that legalized it. But, if anything, the rise in obesity appeared to slow after medical marijuana laws were passed, whereas it appeared to just keep rising in other states, as you can see in the graph below and at 3:45 in my video. 

    The reason pot smokers may be slimmer is because of the effect of smoked marijuana on metabolism. We’ve known for more than nearly 40 years that within 15 minutes of lighting up, our metabolic rate goes up by about 25 percent and stays there for at least an hour, as you can see below and at 4:04 in my video. So, that may be playing a role. 

    Is that why heavy cannabis use is associated with lower bone mineral density and increased risk of fractures? Because users just aren’t as overweight? No. Even when taking BMI into account, heavy cannabis use appears to be “an independent predictor” of weaker bones.

    I originally released a series of marijuana videos in a webinar and downloadable digital DVD. There are still a few videos coming out over the next year, but if you missed any of the already published ones, see the related posts below. 

    For more on bone health, check out the related posts below. 

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    Michael Greger M.D. FACLM

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  • Seasonal Weight Gain in the Fall  | NutritionFacts.org

    Seasonal Weight Gain in the Fall  | NutritionFacts.org

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    SAD doesn’t just stand for the standard American diet.

    There’s a condition known as seasonal affective disorder that is characterized by increased appetite and cravings, as well as greater sleepiness and lethargy, that begins in autumn when light exposure starts to dwindle. This now appears to represent the far end of a normal spectrum of human behavior. We appear to eat more as the days get shorter. There is a “marked seasonal rhythm” to calorie intake with greater meal size, eating rate, hunger, and overall calorie intake in the fall. 

    In preparation for winter, some animals hibernate, doubling their fat stores with autumnal abundance to deal with the subsequent scarcity of winter. Genes have been identified in humans that are similar to hibernation genes, which may help explain why we exhibit some of the same behaviors, and the autumn effect isn’t subtle. As you can see in the graph below and at 1:06 in my video Friday Favorites: Why People Gain Weight in the Fall, researchers calculated a 222-calorie difference between how many calories we consume in the fall versus the spring. This isn’t just because it’s colder, either, since we eat more in the fall than in the winter. It appears we’re just genetically programmed to prep for the deprivation of winter that no longer comes. 

    It’s remarkable that, in this day and age of modern lighting and heating, our bodies would still pick up enough environmental cues of the changing seasons to have such a major influence on our eating patterns. Unsurprisingly, bright light therapy is used to treat seasonal affective disorder, nearly tripling the likelihood of remission, compared to placebo. Though it’s never been tested directly, it can’t hurt to take the dog out for some extra morning and daytime walks in the fall to try to fend off some of the coming holiday season weight gain.

    People blame the holidays for overeating, but it may be that “rather than the holidays causing heightened intake, the seasonal heightening of intake in the fall may have caused the scheduling of holidays at that time.”

    Regardless, as you can see below and at 2:15 in my video, other “specific recommendations for the prevention of obesity and metabolic syndrome by improving the circadian system health,” based on varying degrees of evidence, include: sleeping during the night and being active during the day; sleeping enough—at least seven or eight hours a night; early to bed, early to rise; and short naps are fine. (Contrary to popular belief, daytime napping does not appear to adversely impact sleep at night.) Also recommended: avoiding bright light exposure at night; sleeping in total darkness when possible; making breakfast or lunch your biggest meal of the day; not eating or exercising right before bed; and completely avoiding eating at night. 

    This was the last video in my chronobiology series. If you missed any of the others, check out the related posts below.

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    Michael Greger M.D. FACLM

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  • Phototherapy and Losing Weight  | NutritionFacts.org

    Phototherapy and Losing Weight  | NutritionFacts.org

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    What did randomized controlled trials of phototherapy—bright morning light—for weight loss find? 

    If weakening our circadian rhythm can cause weight gain, might strengthening it facilitate weight loss? You may remember the child’s swing analogy I shared previously. Regular morning meals can give our cycles a little daily push, but the biggest shove comes from our exposure to bright morning light. Similarly, exposure to light at night could be analogous to nighttime eating, as you can see below and at 0:31 in my video Shedding Light on Shedding Weight. 

    Of course, we’ve had candles to illuminate our nights for 5,000 years, but flames from candles, campfires, and oil lamps are “strongly skewed towards the red end of the [light] spectrum; as a result, firelight has much less impact on circadian rhythmicity than electric light.” It’s the shorter blue wavelengths that specially set our circadian clocks. Electric lighting, which we’ve only had for a little over a century, “has gradually changed since the 1960s from an incandescent-bulb form consisting of mainly low-level yellow wavelengths to high-intensity discharge forms,” such as fluorescents and LED lights, “that contain blue wavelengths,” which are more similar to morning sunlight and have the strongest effect on our circadian rhythm.

    Using wrist meters to measure ambient light exposure, researchers found that increased exposure to light in the evening and nighttime correlated with a subsequent increased risk of developing obesity over time. This was presumed to be due to circadian misalignment, but might it instead be a sign of not sleeping as much, and maybe that’s the real reason people grew heavier? This was controlled for in a study of more than 100,000 women, which found that the odds of obesity trended with higher nighttime light exposure independent of sleep duration.

    Compared to women who reported their bedrooms at night were either too dark to see their hand in front of their face or at least dark enough that they couldn’t see across the room, those who reported their bedrooms were light enough to see across the room were significantly heavier. They weren’t all sleeping with nightlights on either. Without blackout curtains on windows, many neighborhoods may be bright enough to cause circadian disruption. Using satellite imagery, scientists have even been able to correlate higher obesity rates with brighter communities. There’s so much light at night these days that, outside of a blackout, the only Milky Way our children will likely ever see is inside a candy wrapper.

    Although sleep quantity could be controlled, what about sleep quality? Maybe people sleeping in bedrooms that aren’t as dim don’t sleep as soundly, leaving them too tired to exercise the next day, for example. You can’t know for sure if nocturnal light exposure is harmful in and of itself until you put it to the test. When that was done, those randomized to exposure to bright light for a few hours in the evenings or exposed even just for a single night suffered adverse metabolic consequences. 

    The more intriguing question then becomes: Can circadian syncing with morning bright light therapy be a viable weight-loss strategy? Insufficient morning light may be the circadian equivalent of skipping breakfast. Indoor lighting is too bright at night, but it may be too dim during the day to robustly boost our daily rhythm. Light exposure from getting outdoors in the morning, even on an overcast day, is correlated to lower body weight compared to typical office lighting, so some doctors started trying “phototherapy” to treat obesity. The first case reports began being published in the 1990s. Three out of four women lost an average of about four pounds over six weeks of morning bright light exposure, but there was no control group to confirm the effect. 

    Ten years later, the first randomized controlled trial was published. Overweight individuals were randomized to an exercise intervention with or without an hour a day of bright morning light. Compared to normal indoor lighting, the bright light group lost more body fat, but it’s possible the light just stimulated them to exercise harder. Studies show that exposure to bright light, even the day prior to exercise, may boost performance. In a handgrip endurance test, exposure to hours of bright light increased the number of contractions until exhaustion from about 770 to 860 the next day. While light-induced improvements in activity or mood can be helpful in their own right, it would be years later still before we finally learned whether the light exposure itself could boost weight loss. 

    Following an unpublished study in Norway purporting to show a dozen-pound weight-loss advantage to eight weeks of 30 minutes of daily daylight (compared to indoor lighting), researchers tried three weeks of 45 minutes of morning bright light compared to the same time sitting in front of an “ion generator” that appeared to turn on but was secretly deactivated. As you can see in the graph below and at 5:08 in my video, the three weeks of light beat out the placebo, but the average difference in body fat reduction was only about a pound. This slight edge didn’t seem to correlate with mood changes, but bright light alone can stimulate serotonin production in the human brain and cause the release of adrenaline-type hormones, both of which could benefit body fat aside from any circadian effects. 

    Regardless of the mechanism, bright morning daylight exposure could present a novel weight-loss strategy straight out of the clear blue sky.  

    I have a whole series on chronobiology. You can see all of the videos on the topic page. The last few are listed below in the related posts and help to paint the full picture of how our environment can affect our circadian rhythms.

    For more on weight loss, you can also check out my recent series in the related posts below, or browse all of my weight loss videos here. 

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    Michael Greger M.D. FACLM

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  • Irregular Meals, Night Shifts, and Metabolic Harms  | NutritionFacts.org

    Irregular Meals, Night Shifts, and Metabolic Harms  | NutritionFacts.org

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    What can shift workers do to moderate the adverse effects of circadian rhythm disruption?

    Shift workers may have higher rates of death from heart disease, stroke, diabetes, dementia, and cardiovascular disease, as well as higher rates of death from cancer. Graveyard shift, indeed! But, is it just because they’re eating out of vending machines or not getting enough sleep? Highly controlled studies have recently attempted to tease out these other factors by putting people on the same diets with the same sleep—but at the wrong time of day. Redistributing eating to the nighttime resulted in elevated cholesterol and increases in blood pressure and inflammation. No wonder shift workers are at higher risk. Shifting meals to the night in a simulated night-shift protocol effectively turned about one-third of the subjects prediabetic in just ten days. Our bodies just weren’t designed to handle food at night, as I discuss in my video The Metabolic Harms of Night Shifts and Irregular Meals.

    Just as avoiding bright light at night can prevent circadian misalignment, so can avoiding night eating. We may have no control over the lighting at our workplace, but we can try to minimize overnight food intake, which has been shown to help limit the negative metabolic consequences of shift work. When we finally do get home in the morning, though, we may disproportionately crave unhealthy foods. In one experiment, 81 percent of participants in a night-shift scenario chose high-fat foods, such as croissants, out of a breakfast buffet, compared to just 43 percent of the same subjects during a control period on a normal schedule.

    Shiftwork may also leave people too fatigued to exercise. But, even at the same physical activity levels, chronodisruption can affect energy expenditure. Researchers found that we burn 12 to 16 percent fewer calories while sleeping during the daytime compared to nighttime. Just a single improperly-timed snack can affect how much fat we burn every day. Study subjects eating a specified snack at 10:00 am burned about 6 more grams of fat from their body than on the days they ate the same snack at 11:00 pm. That’s only about a pat and a half of butter’s worth of fat, but it was the identical snack, just given at a different time. The late snack group also suffered about a 9 percent bump in their LDL cholesterol within just two weeks.

    Even just sleeping in on the weekends may mess up our metabolism. “Social jetlag is a measure of the discrepancy in sleep timing between our work days and free days.” From a circadian rhythm standpoint, if we go to bed late and sleep in on the weekends, it’s as if we flew a few time zones west on Friday evening, then flew back Monday morning. Travel-induced jet lag goes away in a few days, but what might the consequences be of constantly shifting our sleep schedule every week over our entire working career? Interventional studies have yet put it to the test, but population studies suggest that those who have at least an hour of social jet lag a week (which may describe more than two-thirds of people) have twice the odds of being overweight. 

    If sleep regularity is important, what about meal regularity? “The importance of eating regularly was highlighted early by Hippocrates (460–377 BC) and later by Florence Nightingale,” but it wasn’t put to the test until the 21st century. A few population studies had suggested that those eating meals irregularly were at a metabolic disadvantage, but the first interventional studies weren’t published until 2004. Subjects were randomized to eat their regular diets divided into six regular eating occasions a day or three to nine daily occasions in an irregular manner. Researchers found that an irregular eating pattern can cause a drop in insulin sensitivity and a rise in cholesterol levels, as well as reduce the calorie burn immediately after meals in both lean and obese individuals. The study participants ended up eating more, though, on the irregular meals, so it’s difficult to disentangle the circadian effects. The fact that overweight individuals may overeat on an irregular pattern may be telling in and of itself, but it would be nice to see such a study repeated using identical diets to see if irregularity itself has metabolic effects.

    Just such a study was published in 2016: During two periods, people were randomized to eat identical foods in a regular or irregular meal pattern. As you can see in the graph below and at 4:47 in my video, during the irregular period, people had impaired glucose tolerance, meaning higher blood sugar responses to the same food.

    They also had lower diet-induced thermogenesis, meaning the burning of fewer calories to process each meal, as seen in the graph below and at 4:55 in my video.

    The difference in thermogenesis only came out to be about ten calories per meal, though, and there was no difference in weight changes over the two-week periods. However, diet-induced thermogenesis can act as “a satiety signal.” The extra work put into processing a meal can help slake one’s appetite. And, indeed, “lower hunger and higher fullness ratings” during the regular meal period could potentially translate into better weight control over the long term. 

    The series on chronobiology is winding down with just two videos left in this series: Shedding Light on Shedding Weight and Friday Favorites: Why People Gain Weight in the Fall.

    If you missed any of the other videos, see the related posts below. 
     

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    Michael Greger M.D. FACLM

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  • Circadian Rhythms and Our Blood Sugar Levels  | NutritionFacts.org

    Circadian Rhythms and Our Blood Sugar Levels  | NutritionFacts.org

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    The same meal eaten at the wrong time of day can double blood sugar. 

    We’ve known for more than half a century that our glucose tolerance—the ability of our body to keep our blood sugars under control—declines as the day goes on. As you can see in the graph below and at 0:25 in my video How Circadian Rhythms Affect Blood Sugar Levels, if you hook yourself up to an IV and drip sugar water into your vein at a steady pace throughout the day, your blood sugars will start to go up at about 8:00 pm, even though you haven’t eaten anything and the infusion rate didn’t change.

    The same amount of sugar is going into your system every minute, but your ability to handle it deteriorates in the evening before bouncing right back in the morning. A meal eaten at 8:00 pm can cause twice the blood sugar response as an identical meal eaten at 8:00 am, as shown in the graph below and at 0:51 in my video. It’s as if you ate twice as much. Your body just isn’t expecting you to be eating when it’s dark outside. Our species may have only discovered how to use fire about a quarter million years ago. We just weren’t built for 24-hour diners. 

    One of the tests for diabetes is called the glucose tolerance test, which sees how fast our body can clear sugar from our bloodstream. You swig down a cup of water with about four and a half tablespoons of regular corn syrup mixed in, then have your blood sugar measured two hours later. By that point, your blood sugar should be under 140 mg/dL. Between 140 and 199 is considered to be a sign of prediabetes, and 200 and up is a sign of full-blown diabetes, as you can see in the graph below and at 1:37 in my video. 

    The circadian rhythm of glucose tolerance is so powerful that a person can test normal in the morning but as a prediabetic later in the day. Prediabetics who average 163 mg/dL at 7:00 am may test out as frank diabetics at over 200 mg/dL at 7:00 pm, as you can see in the graph below and at 1:53 in my video. 

    Choosing lower glycemic foods may help promote weight loss, but timing is critical. Due to this circadian pattern in glucose tolerance, a low-glycemic food at night can cause a higher blood sugar spike than a high-glycemic food eaten in the morning, as you can see below and at 2:05 in my video.

    We’re so metabolically crippled at night that researchers found that eating a bowl of All Bran cereal at 8:00 pm caused as high a blood sugar spike as eating Rice Krispies at 8:00 am, as you can see in the graph below and at 2:23 in my video.

    High glycemic foods at night would seem to represent the worst of both worlds. So, if you’re going to eat refined grains and sugary junk, it might be less detrimental in the morning, as you can see in the graph below and at 2:32 in my video.  

    The drop in glucose tolerance over the day could therefore help explain the weight-loss benefits of frontloading calories towards the beginning of the day. Even just taking lunch earlier versus later may make a difference, as you can see in the graph below and at 2:48 in my video.

    People randomized to eat a large lunch at 4:30 pm suffered a 46 percent greater blood sugar response compared to an identical meal eaten just a few hours earlier at 1:00 pm. A meal at 7:00 am can cause 37 percent lower blood sugars than an identical meal at 1:00 pm, as you can see below, and at 3:04 in my video.

    Now, there doesn’t seem to be any difference between a meal at 8:00 pm and the same meal at midnight; they both seem to be too late, as you can see below, and at 3:15 in my video.

    But, eating that late, at midnight or even 11:00 pm, can so disrupt your circadian rhythm that it can mess up your metabolism the next morning, resulting in significantly higher blood sugars after breakfast, compared to eating the same dinner at 6:00 pm the evening before, as shown in the graph below and at 3:32 in my video.

    So, these revelations of chronobiology bring the breakfast debate full circle. Skipping breakfast not only generally fails to cause weight loss, but it worsens overall daily blood sugar control in both diabetic individuals and people who are not diabetic, as you can see in the graph below and at 3:44 in my video.

    Below and at 3:53, you can see a graph showing how the breakfast skippers have higher blood sugars even while they’re sleeping 20 hours later. This may help explain why those who skip breakfast appear to be at higher risk of developing type 2 diabetes in the first place. 

    Breakfast skippers also tend to have higher rates of heart disease, as well as having higher rates of atherosclerosis, in general. Is this just because “skipping breakfast tends to cluster with other unhealthy choices, including smoking” and sicklier eating habits overall? The link between skipping breakfast and heart disease—even premature death in general—seems to survive attempts to control for these confounding factors, but you don’t really know until you put it to the test.

    Does skipping breakfast lead to higher cholesterol, for example? Yes, researchers found a significant rise in LDL (bad) cholesterol in study participants randomized to skip breakfast; they were about 10 points higher within just two weeks, as you can see below and at 4:45 in my video.

    The Israeli study with the caloric distribution of 700 calories for breakfast, 500 for lunch, and 200 for dinner that I’ve discussed previously found that the triglycerides of the king-prince-pauper group (those eating more at breakfast versus dinner) got significantly better—a 60-point drop—while those of the pauper-prince-king group got significantly worse (a 26-point rise). So, consuming more calories in the morning relative to the evening may actually have a triple benefit: more weight loss, better blood sugar control, and lower heart disease risk, as you can see below and at 5:18 in my video. 

    If you’re going to skip any meal, whether you’re practicing intermittent fasting or time-restricted feeding (where you try to fit all of your food intake into a certain time window each day), it may be safer and more effective to skip dinner rather than breakfast.

    I’m back with the next installment of the chronobiology series! I previously explored eating breakfast for weight loss (Is Breakfast the Most Important Meal for Weight Loss? and Is Skipping Breakfast Better for Weight Loss?), introduced chronobiology (How Circadian Rhythms Can Control Your Health and Weight), and looked at the science on eating more in the mornings than the evenings (Eat More Calories in the Morning to Lose Weight, Breakfast Like a King, Lunch Like a Prince, Dinner Like a Pauper, and Eat More Calories in the Morning Than the Evening).

    Next, you’ll see How to Sync Your Central Circadian Clock to Your Peripheral Clocks.

    The series will wrap up in the next couple of weeks. See videos and blogs in related posts below.

    Note: The Israeli 700/500/200 study that I mentioned is detailed in the Breakfast Like a King, Lunch Like a Prince, Dinner Like a Pauper video if you want to know more. Also, check the corresponding blog in related posts. 

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    Michael Greger M.D. FACLM

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  • Morning Calories vs. Evening Calories  | NutritionFacts.org

    Morning Calories vs. Evening Calories  | NutritionFacts.org

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    Why are calories eaten in the morning less fattening than calories eaten in the evening? 

    One reason calories consumed in the morning are less fattening than those eaten in the evening is that more calories are burned off in the morning due to diet-induced thermogenesis. That’s the amount of energy the body takes to digest and process a meal, given off in part as waste heat. If people are given the same meal in the morning, afternoon, or night, their body uses up about 25 percent more calories to process it in the afternoon than at night and about 50 percent more calories to digest it in the morning, as you can see below and at 0:36 in my video Eat More Calories in the Morning Than the Evening. That leaves fewer net calories in the morning to be stored as fat.

    Let’s put some actual numbers to it. A group of Italian researchers randomized 20 people to eat the same standardized meal at either 8:00 am or 8:00 pm and had them return a week later to do the opposite. So, each person had a chance to eat the same meal for breakfast and dinner. After every meal, the study participants were placed in a “calorimeter” contraption to precisely measure how many calories they were burning over the next three hours. As you can see below and at 1:18 in my video, the researchers calculated that the meal given in the morning took about 300 calories to digest, whereas the same meal given at night only used up about 200 calories to process. The meal was about 1,200 calories, but, when eaten in the morning, it ended up only providing about 900 calories compared to more like 1,000 calories at night. Same meal, same food, same amount of food, but effectively 100 fewer calories when consumed in the morning rather than at night. So, a calorie is not just a calorie. It depends on when we eat it. 

    But why do we burn more calories when eating a morning meal? Is it behavioral or biological? If you started working the graveyard shift, sleeping during the day and working all night, which meal would net you fewer calories? Would it be the “breakfast” you had at night before you went to work or the “dinner” you had in the morning before you went to bed? In other words, is it something about eating before you go to sleep that causes your body to hold onto more calories, or is it built into our circadian rhythm, where we store more calories at night regardless of what we’re doing? You don’t know until you put it to the test.

    Harvard researchers randomized people to identical meals at 8:00 am versus 8:00 pm while under simulated night shifts or day shifts. Regardless of activity level or sleeping cycle, the number of calories that were burned processing the morning meals was 50 percent higher than in the evening, as you can see in the graph below and at 2:45 in my video. So, the difference is explained by chronobiology: It’s just part of our circadian rhythm to burn more meal calories in the morning. But, why? What exactly is going on? 

    How does it make sense for our body to waste calories in the morning when we have the whole day ahead of us? 

    Our body isn’t so much wasting calories as investing them. When we eat in the morning, our body bulks up our muscles with glycogen, which is the primary energy reserve our body uses to fuel our muscles, but this takes energy. In the evening, our body expects to be sleeping for much of the next 12 hours, so rather than storing blood sugar as extra glycogen in our muscles, it preferentially uses it as an energy source, which may end up meaning we burn less of our backup fuel (body fat). In the morning, however, our body expects to be running around all day, so instead of just burning off breakfast, our body continues to dip into its fat stores while we use breakfast calories to stuff our muscles full of the energy reserves we need to move around over the day. That’s where the “inefficiency” may come from. The reason it costs more calories to process a morning meal is that, instead of just burning glucose (blood sugar) directly, our body uses up energy to string glucose molecules together into chains of glycogen in our muscles, which are then just going to be broken back down into glucose later in the day. That extra assembly/disassembly step takes energy—energy that our body takes out from the meal, leaving us with fewer calories.

    So, in the morning, our muscles are especially sensitive to insulin, rapidly pulling blood sugar out of our bloodstream to build up glycogen reserves. At night, though, our muscles become relatively insulin-resistant and resist the signal to take in extra blood sugar. So, does that mean you get a higher blood sugar and insulin spike in the evening compared to eating the same meal in the morning? Yes. As you can see in the graph below and at 5:02 in my video, in that 100-calorie-difference study, for example, blood sugars rose twice as high after the 8:00 pm meal compared to the same meal eaten in the morning.

    So, shifting the bulk of our caloric intake towards the morning would appear to have a dual benefit—more weight loss, and better blood sugar control, as shown in the graph below and at 5:12 in my video. 

    If you thought dual benefits sounded good, stay tuned for triple benefits! I dive deeper into circadian rhythms. See related posts below.

    My last few videos (see below) focus on why science points to loading your calories towards the beginning of the day.

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    Michael Greger M.D. FACLM

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  • Fighting Cancer and the Common Cold with Garlic  | NutritionFacts.org

    Fighting Cancer and the Common Cold with Garlic  | NutritionFacts.org

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    Raw garlic is compared to roasted, stir-fried, simmered, and jarred garlic.

    Garlic lowers blood pressure, regulates cholesterol, and stimulates immunity. I’ve talked before about its effect on heart disease risk factors, but what about immunity? Eating garlic appears to offer the best of both worlds, dampening the overreactive face of the immune system by suppressing inflammation while boosting protective immunity—for example, the activity of our natural killer cells, which our body uses to purge cells that have been stricken by viruses or cancer. “In World War II garlic was called ‘Russian Penicillin’ because, after running out of antibiotics, the soviet government turned to these ancient treatments for its soldiers,” but does it work? You don’t know until you put it to the test.

    How about preventing the common cold? As I discuss in my video Benefits of Garlic for Fighting Cancer and the Common Cold, it is perhaps “the world’s most widespread viral infection, with most people suffering approximately two to five colds per year.” In the first study “to use a double-blind, placebo-controlled design to investigate prevention of viral disease with a garlic supplement,” those randomized to the garlic suffered 60 percent fewer colds and were affected 70 percent fewer days. So, those on garlic not only had fewer colds, but they also recovered faster, suffering only one and a half days instead of five. Accelerated relief, reduced symptom severity, and faster recovery to full fitness. Interesting, but that study was done about two decades ago. What about all of the other randomized controlled trials? There aren’t any. There’s only that one trial to date. Still, the best available balance of evidence suggests that, indeed, “garlic may prevent occurrences of the common cold.”

    What about cancer? Is garlic “a stake through the heart of cancer?” As you can see below and at 2:05 in my video, various garlic supplements have been tested on cells in a petri dish or lab animals, but there weren’t any human studies to see if garlic could affect gene expression until now. 

    Researchers found that if you eat one big clove’s worth of crushed raw garlic, you get an alteration of the expression of your genes related to anti-cancer immunity within hours. You can see a big boost in the production of cancer-suppressing proteins like oncostatin when you drip garlic directly on cells in a petri dish, as shown in the graph below and at 2:25 in my video.   

    What’s more, you can also see boosted gene expression directly in your bloodstream within three hours of eating it, as seen below and at 2:34 in my video. Does this then translate into lower cancer risk?

    As you can see in the graph below and at 2:44 in my video, after putting together ten population studies, researchers found that those reporting higher consumption of garlic only had half the risk of stomach cancer.

    How do you define “high” garlic consumption? Each study was different, from a few times a month to every day. Regardless, those who ate more garlic appeared to have lower cancer rates than those who ate less, suggesting a protective effect. Stomach cancer is a leading cause of cancer-related death around the world, and garlic “is relatively cheap; the product is freely available and easy to incorporate into a daily diet in a palatable manner”—and safely, too, so why not? And, perhaps, the more, the better. 

    The only way to prove garlic can prevent cancer is to put it to the test. Thousands of individuals were randomized to receive seven years of a garlic supplement or a placebo. Those getting garlic did tend to get less cancer and die from less cancer, as you can see below and at 3:35 in my video, but the findings were not statistically significant, meaning that could have just happened by chance. 

    Why didn’t we see a more definitive result, given that garlic eaters appear to have much lower cancer rates? Well, the researchers didn’t give them garlic; they gave them garlic extract and oil pills. It’s possible that some of the purported active components weren’t preserved in supplement form. Indeed, one study of garlic supplements, for example, found that it might take up to 27 capsules to obtain the same amount of garlic goodness found in just half a clove of crushed raw garlic.  

    What happens if you cook garlic? If you compare raw chopped garlic to garlic simmered for 15 minutes, boiled for 6 minutes, or stir-fried for just 1 minute, you can get a three-fold drop in one of the purported active ingredients called allicin when you boil it, even more of a loss if you simmer it too long, and seemingly total elimination by even a single minute of stir-frying, as seen below and at 4:21 in my video. What about roasted garlic? Surprisingly, even though roasting is hotter than boiling, that cooking method preserved about twice as much. Raw garlic has the most, but it may be easier for some folks to eat two to three cloves of cooked garlic than even half a clove of raw. 

    What about pickled garlic or those jars of minced garlic packed in water or oil? Fancy, fermented black garlic? Though jarred garlic may be more convenient, they have comparatively less garlicky goodness, especially pickled garlic, and the black garlic falls far behind, as you can see in the graph below and at 5:12 in my video. 

    Can you eat too much? The garlic meta-analysis suggests there are no real safety concerns with side effects or overdosing, though that’s with internal use. You should not stick crushed garlic on your skin. It can cause irritation and, if left on long enough, can actually burn you. Wrap your knees with a garlic paste bandage or stick some on your back overnight, and you can end up burned, as seen below, and at 5:42 and 5:44 in my video.  

    Definitely don’t rub garlic on babies, even if you see an online article saying that topical garlic is good for respiratory disorders and your little one is congested. Below and at 5:57 in my video, you can see the blisters she got. The poor pumpkin! “It is crucial…to explain to patients that ‘natural’ does not equal ‘safe’…” 

    Don’t put it on your toes, don’t use it as a face mask, and don’t use it to try to get out of military service either.  

    If you just eat it like you’re supposed to, there shouldn’t be a problem. Some people can get an upset stomach if they eat too much, though, and you can’t really say there aren’t any side effects, given the “body odor and bad breath.”

    The other video I mentioned is Friday Favorites: Benefits of Garlic Powder for Heart Disease. What else can garlic do? See related posts below.

    And, for more on specific foods for fighting colds and cancer, check out related posts below. 

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    Michael Greger M.D. FACLM

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  • Lose Weight by Eating More in the Morning  | NutritionFacts.org

    Lose Weight by Eating More in the Morning  | NutritionFacts.org

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    A calorie is not a calorie. It isn’t only what you eat, but when you eat.

    Mice are nocturnal creatures. They eat during the night and sleep during the day. However, if you only feed mice during the day, they gain more weight than if they were fed a similar amount of calories at night. Same food and about the same amount of food, but different weight outcomes, as you can see in the graph below and at 0:18 in my video Eat More Calories in the Morning to Lose Weight, suggesting that eating at the “wrong” time may lead to disproportionate weight gain. In humans, the wrong time would presumably mean eating at night. 

    Recommendations for weight management often include advice to limit nighttime food consumption, but this was largely anecdotal until it was first studied experimentally in 2013. Researchers instructed a group of young men not to eat after 7:00 pm for two weeks. Compared to a control period during which they continued their regular habits, they ended up about two pounds lighter after the night-eating restriction. This is not surprising, given that dietary records show the study participants inadvertently ate fewer calories during that time. To see if timing has metabolic effects beyond just foreclosing eating opportunities, you’d have to force people to eat the same amount of the same food, but at different times of the day. The U.S. Army stepped forward to carry out just such an investigation.

    In their first set of experiments, Army researchers had people eat a single meal a day either as breakfast or dinner. The results clearly showed the breakfast group lost more weight, as you can see in the graph below and at 1:35 in my video. When study participants ate only once a day at dinner, their weight didn’t change much, but when they ate once a day at breakfast, they lost about two pounds a week. 

    Similar to the night-eating restriction study, this is to be expected, given that people tend to be hungrier in the evening. Think about it. If you went nine hours without eating during the day, you’d be famished, but people go nine hours without eating overnight all the time and don’t wake up ravenous. There is a natural circadian rhythm to hunger that peaks around 8:00 pm and drops to its lowest level around 8:00 am, as you can see in the graph below and at 2:09 in my video. That may be why breakfast is typically the smallest meal of the day. 

    The circadian rhythm of our appetite isn’t just behavioral, but biological, too. It’s not just that we’re hungrier in the evening because we’ve been running around all day. If you stayed up all night and slept all day, you’d still be hungriest when you woke up that evening. To untangle the factors, scientists used what’s called a “forced desynchrony” protocol. Study participants stayed in a room without windows in constant, unchanging, dim light and slept in staggered 20-hour cycles to totally scramble them up. This went on for more than a week, so the subjects ended up eating and sleeping at different times throughout all phases of the day. Then, the researchers could see if cyclical phenomena are truly based on internal clocks or just a consequence of what you happen to be doing at the time.  

    For instance, there is a daily swing in our core body temperature, blood pressure, hormone production, digestion, immune activity, and almost everything else, but let’s use temperature as an example. As you can see in the graph below and at 3:21 in my video, our body temperature usually bottoms out around 4:00 am, dropping from 98.6°F (37°C) down to more like 97.6°F (36.4°C). Is this just because our body cools down as we sleep? No. By keeping people awake and busy for 24 hours straight, it can be shown experimentally that it happens at about the same time no matter what. It’s part of our circadian rhythm, just like our appetite. It makes sense, then, if you are only eating one meal per day and want to lose weight, you’d want to eat in the morning when your hunger hormones are at their lowest level. 

    Sounds reasonable, but it starts to get weird.

    The Army scientists repeated the experiment, but this time, they had the participants eat exactly 2,000 calories either as breakfast or as dinner, taking appetite out of the picture. The subjects weren’t allowed to exercise either. Same number of calories, so the same change in weight, right? No. As you can see in the graph below and at 4:18 in my video, the breakfast-only group still lost about two pounds a week compared to the dinner-only group. Two pounds of weight loss eating the same number of calories. That’s why this concept of chronobiology, meal timing—when to eat—is so important. 

    Isn’t that wild? Two pounds of weight loss a week eating the same number of calories! That was a pretty extreme study, though. What about just shifting a greater percentage of calories to earlier in the day? That’s the subject of my next video: Breakfast Like a King, Lunch Like a Prince, Dinner Like a Pauper. First, let’s take a break from chronobiology to look at the Benefits of Garlic for Fighting Cancer and the Common Cold. Then, we’ll resume checking other videos in the related posts below.

    If you missed the first three videos in this extended series, also check out related posts below. 

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    Michael Greger M.D. FACLM

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  • Milk Hormones and Female Infertility  | NutritionFacts.org

    Milk Hormones and Female Infertility  | NutritionFacts.org

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    Dairy consumption is associated with years of advanced ovarian aging, thought to be due to the steroid hormones or endocrine-disrupting chemicals in cow’s milk.
     
    When it comes to the amount of steroid hormones we are exposed to in the food supply, dairy “milk products supply about 60–80% of ingested female sex steroids.” I’ve talked about the effects of these estrogens and progesterone in men and prepubescent children, and how milk intake can spike estrogen levels within hours of consumption. You can see graphs illustrating these points from 0:25 in my video The Effects of Hormones in Milk on Infertility in Women. In terms of effects on women, I’ve discussed the increased endometrial cancer risk in postmenopausal women. What about reproductive-age women? Might dairy hormones affect reproduction? 
     
    We’ve known that “dairy food intake has been associated with infertility; however, little is known with regard to associations with reproductive hormones or anovulation.” How might dairy do it? By affecting how the uterus prepares, or by affecting the ovary itself? Researchers found that women who ate yogurt or cream had about twice the risk of sporadic anovulation, meaning failure of ovulation, so some months there was no egg to fertilize at all. Now, we know most yogurt is packed with sugar these days. Even plain Greek yogurt can have more sugar than a double chocolate glazed cake donut, but the researchers controlled for that and the results remained after adjusting for the sugar content, “which suggests that the risk of anovulation was independent of the sugar content included in many flavored yogurt products.” We don’t know if this was just a fluke or exactly what the mechanism might be, but if women skip ovulation here and there throughout their lives, might they end up with a larger ovarian reserve of eggs? 
     
    Women are starting to have their first baby later in life. As you can see in the graph below and at 2:02 in my video, there’s been a rise in women having babies when they’re in their late 30s and 40s.

    We used to think that women’s ovarian reserve of eggs stayed relatively stable until a rapid decline at about age 37, but now we know it appears to be more of a gradual loss of eggs over time. The graph below and at 2:22 in my video charts a steady loss starting at peak fertility in one’s 20s.

    This measures “antral follicle count,” which is an ultrasound test where you can count the number of “next batter up” eggs in the ovaries, as you can see below and at 2:31 in my video. It is probably the best reflection of true reproductive age. It’s a measure of ovarian reserve—how many eggs a woman has left.

    What does this have to do with diet? Researchers at Harvard looked at the association of various protein intakes with ovarian antral follicle counts among women having trouble getting pregnant. “Even though diminished ovarian reserve is one of the major causes of female infertility, the process leading to reproductive senescence [deterioration with age] currently is poorly understood. In light of emerging population trends towards delayed pregnancy, the identification of reversible factors (including diet) that affect the individual rates of reproductive decline might be of significant clinical value.”

    The researchers performed ultrasounds on all the women, studied their diets, and concluded that higher intake of dairy protein was associated with lower antral follicle counts—in other words, accelerated ovarian aging. The graph below and at 3:39 in my video shows what counts look like in nonsmokers: Significantly lower ovarian reserve (12.7 antral follicle counts) at the highest dairy intake, which would be like three ounces of cheese a day, compared to the lowest dairy intake (16.9 antral follicle counts).

    What do these numbers mean in terms of biological age? Is 16.9 down to 12.7 really that much of a difference? As you can see below and at 3:58 in my video, when you look at women with really robust ovaries, a follicle count of 16.9 is what you might see in a 36- or 37-year-old, whereas 12.7, which is what you can see in women eating the most dairy, is what you might see in a really fertile 50-year-old. So, we’re talking year’s worth of ovarian aging between the highest and lowest dairy consumers.

    While it wasn’t possible for the researchers to “identify the underlying mechanism linking higher dairy protein intake to lower AFC,” antral follicle count, they had educated guesses. (1) It could be the steroid hormones and growth factors or (2) “the contamination of milk products by pesticides and endocrine disrupting chemicals that may negatively impact” the development of these ovarian follicles and egg competence.

    “Regarding the former [the hormones], studies suggest that commercial milk (derived from both pregnant and non-pregnant animals) contains large amounts of estrogens, progesterone, and other placental hormones that are eventually released into the human food chain, with dairy intake accounting for 60–80% of the estrogens consumed. Dairy estrogens overcome [survive] processing, appear in raw whole cow’s and commercial milk products, are found in substantially higher concentrations with increasing amounts of milk fat, with no apparent difference between organic and conventional dairy products…” Hormones are just naturally in cows’ bodies, so they aren’t just in the ones injected with growth hormones. And, once these bovine hormones are inside the human body, they get converted to estrone and estradiol, the main active human estrogens. Following absorption, bovine steroids may then affect reproductive outcomes.

    The researchers asserted that further studies are needed and that “it is imperative that these findings are reproduced in prospective studies designed to clarify the biology underlying the observed associations. The latter might be crucial given that consumption of another species’ milk by humans is an evolutionary novel dietary behavior that has the potential to alter reproductive parameters and may have long-term adverse health effects.”

    The video I mentioned about the effects of these estrogens and progesterone in men and prepubescent children is The Effects of Hormones in Dairy Milk on Cancer.

    I talk about the effect of dairy estrogen on male fertility in Dairy Estrogen and Male Fertility.

    How else might diet affect fertility? See related posts below. 

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    Michael Greger M.D. FACLM

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  • Skip Breakfast to Lose Weight?  | NutritionFacts.org

    Skip Breakfast to Lose Weight?  | NutritionFacts.org

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    Breakthroughs in the field of chronobiology—the study of our circadian rhythms—help solve the mystery of the missing morning calories in breakfast studies.

    Where did this whole “breakfast is the most important meal of the day” concept come from? “The Father of Public Relations,” Edward Bernays, infamous for his “Torches of Freedom” campaign to get women to start smoking back in the 1920s, was paid by a bacon company to popularize the emblematic bacon-and-eggs breakfast. The role of public relations, he wrote in his book Propaganda, is the “conscious and intelligent manipulation of the organized habits and opinions of the masses….” Public relations specialists thereby “constitute an invisible government, which is the true ruling power of our country….”

    Breakfast is big business. Powerful corporate interests, such as the cereal lobby, are blamed for “perpetuating myths such as the value of consuming breakfast.” An editorial in The American Journal of Clinical Nutrition urged nutrition scientists to speak truth to power and challenge conventional wisdom when necessary “even when it looks like we are taking away motherhood and apple pie.” “Actually,” the editorial concludes, “reducing the portion size of apple pie might not be a bad idea, either.”

    So, should we “break the feast” and skip breakfast to lose weight? As I discuss in my video Is Skipping Breakfast Better for Weight Loss?, though “the advice to eliminate breakfast will surely pit…nutritional scientists…against the very strong and powerful food industry,” skipping breakfast has been described as “a straightforward and feasible strategy to reduce total daily energy [caloric] intake.” Unfortunately, it doesn’t seem to work.

    Most randomized controlled studies of breakfast skipping found no weight-loss benefit to omitting breakfast. How is that possible if skipping breakfast means skipping calories? The Bath Breakfast Project, a famous series of experiments run not out of a tub, but the University of Bath in the UK, discovered a key to the mystery. Men and women were randomized to either eat breakfast (defined as taking in at least 700 calories before 11:00 am) or fast until noon every day. As you can see in the graph below and at 2:15 in my video, as in other similar trials, the breakfast-eating group ate a little less throughout the rest of the day but still ended up with hundreds of excess daily calories over the breakfast skippers.

    Those who ate breakfast consumed more than 500 more calories a day. Over six weeks, that would add up to more than 20,000 extra calories. Yet, after six weeks, both groups ended up with the same change in body fat, as you can see below and at 2:36 in my video. How could tens of thousands of calories just effectively disappear? 

    If more calories were going in with no change in weight, then there must have been more calories going out. And, indeed, as you can see in the graph below at 2:52 and in my video, the breakfast group was found to spontaneously engage in more light-intensity physical activity in the mornings than the breakfast-skipping group. Light-intensity activities include things like casual walking or light housecleaning, not structured exercise per se, but apparently, enough extra activity to use up the bulk of those excess breakfast calories. There’s a popular misconception that our body goes into energy conservation mode when we skip breakfast by slowing our metabolic rate. However, that does not appear to be true. But, maybe our body does intuitively slow us down in other ways. When we skip breakfast, our bodies just don’t seem to want to move around as much. 

    The extra activity didn’t completely make up for the added calories consumed by the breakfast group, though. We seem to still be missing about a hundred daily calories, suggesting there may be another factor to account for the mystery of the MIA morning calories. Recent breakthroughs in the field of chronobiology—the study of our body’s natural rhythms—have unsettled an even more sacred cow of nutrition dogma: the concept that a calorie is a calorie. It’s not just what we eat, but when we eat. Same number of calories, different weight loss, depending on meal timing.  

    Just to give you a taste: As you can see in the graph below and at 4:11 in my video, the exact same number of calories at breakfast are significantly less fattening than the same number of calories eaten at supper. Mind-blowing!

    A diet with a bigger breakfast causes more weight loss than the same diet with a bigger dinner, as shown below and at 4:23 in my video. Because of our circadian rhythms, morning calories don’t appear to count as much as evening calories. So, maybe breakfast should be the most important meal of the day after all. 

    If you missed my last video, catch up with Flashback Friday: Is Breakfast the Most Important Meal for Weight Loss or Should It Be Skipped?. 

    Did I pique your interest in chronobiology? If so, you’re in luck. See more in the related posts below. 

    For some breakfast inspiration, check out A Better Breakfast and my recipe videos for a vegetable smoothie and a grain bowl from The How Not to Die Cookbook. 

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    Michael Greger M.D. FACLM

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

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

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

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

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

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


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

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


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


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

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

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    Michael Greger M.D. FACLM

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  • ‘Gut Health’ Has a Fatal Flaw

    ‘Gut Health’ Has a Fatal Flaw

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    In my childhood home, an often-repeated phrase was “All disease begins in the gut.” My dad, a health nut, used this mantra to justify his insistence that our family eat rice-heavy meals, at the exact same time every day, to promote regularity and thus overall health. I would roll my eyes, dubious that his enthusiasm for this practice was anything more than fussiness.

    Now, to my chagrin, his obsession has become mainstream. Social-media testimonials claim that improving your “gut health” not only helps with stomach issues such as bloating and pain but also leads to benefits beyond the gastrointestinal system (easing problems including, but not limited to, itching, puffy face, slow-growing hair, low energy, acne, weight gain, and anxiety). You can now find a staggering range of products claiming to support digestive health: Joining traditionally gut-friendly fermented foods such as yogurt and sauerkraut are “probiotic” or “prebiotic” teas, cookies, gummies, supplements, powders, and even sodas.

    The reality is less straightforward. Maintaining the health of the gastrointestinal tract, like the health of any body part, is always a good idea. But expecting certain foods and products to overhaul gut health is unrealistic, as is believing that they will guarantee greater overall well-being. Those claims are “a little bit premature,” Karen Corbin, an investigator at the Translational Research Institute of Metabolism and Diabetes, told me. Obsessing over it just isn’t worth the trouble, and can even do more harm than good. “Gut health” cookies, after all, are still cookies.

    In my dad’s defense, your gut does matter for your health. A massive microbial civilization lives mostly along the large intestine, helping the body get the most out of food. Broadly, a healthy gut is one where the different segments of this population—numerous species of bacteria, fungi, and viruses—live in harmony. An unhealthy one implies a disturbance of the peace: One group may grow too powerful, or an invading microbe may throw things off-balance, leading to problems including gastroenteritis and a compromised immune system.

    Diet in particular has a profound impact on the gut—and how it subsequently makes you feel. “Food can have effects on the microbiome, which can then secondarily affect the host,” Purna Kashyap, a gastroenterologist at the Mayo Clinic, told me. The effects of food on a person and their microbes, he added, are generally congruent; fast food, for example, is “bad for both of us.” Neglect to feed your microbiome and the balance of microbes could tip into disarray, resulting in an imbalanced gut and corresponding bloating, stomach pain, and problems with bowel movements.

    Fermented foods such as yogurt and kimchi, long considered good for digestive health, are known as “probiotics” because they contain live bacteria that take up residence in your gut. Other foods are considered “prebiotic” because they feed the microbes already in your gut—mostly fiber, because it isn’t digested in the stomach. Getting more fiber improves regularity and supports a more normal GI system, Corbin said.

    But the fundamental problem with the gut-health obsession is that “there’s no clear definition of a healthy gut microbiome,” Corbin said. The makeup and balance of people’s microbiomes vary based on numerous factors, including genes, diet, environment, and even pets. This means that a treatment that works to rebalance one gut might not work for another. It also means that a product promoting a healthy gut doesn’t mean anything concrete. The idea that achieving gut health, however it’s defined, can solve stomach-related issues is misguided; many diseases can cause abdominal distress.

    Less certain is how much gut health is responsible for benefits beyond the gastrointestinal tract. No doubt the microbiome is connected to other parts of the body; recent research has suggested that it has a role in weight gain, depression, and even cancer, supporting the idea that having a healthy gut could lead to other benefits. But the mechanisms underpinning them are largely unknown. Which microbes are involved? What are they doing? There are “a lot of tall claims based on animal studies that the microbiome influences diabetes or obesity or whatever,” and the translatability of those studies to humans is “really unlikely,” Daniel Freedberg, a gastroenterologist at Columbia University, told me. Until scientists can show definitively that microbe X leads to outcome Y, Corbin said, any relationships between the gut and overall health are “just correlations.”

    None of this is to say that paying more attention to your digestive health is a bad idea. Especially for people diagnosed with gastrointestinal problems like IBS or Crohn’s disease, it can be essential. For everyone else, pursuing a healthy gut with food and supplements can be a nonspecific process with poorly defined goals. The food industry has capitalized on interest in probiotics and prebiotics—as well as lesser-known postbiotics and synbiotics—making products such as “insanely probiotic” yogurt, probiotic-fortified chocolate and spaghetti, and prebiotic sodas. Particularly with probiotics, the specifics are lacking. Which bacteria, and how many of them, actually make it past the stomach into the colon isn’t well understood. “A lot of probiotics are unlikely to contain viable bacteria, and probably very few of them are really making it through to the colon,” Freedberg said.

    Prebiotics are generally more important, although the source matters. Prebiotic fiber is “one of the most important things that determines what bacteria are there,” Freedberg told me, but getting small amounts from fiber-fortified products isn’t going to make a huge difference. The soda brands Poppi and Olipop largely contain inulin, a type of fiber that’s common in food manufacturing for its slightly sweet taste, Freedberg explained, though it probably doesn’t contain a lot, otherwise it would become “sludgy.” Olipop contains about nine grams of fiber per can, roughly the same amount as one cup of cooked lima beans.

    Of course, any product that is inherently unhealthy won’t magically become good for you the moment fiber or live bacteria are added to it. With desserts and salty snacks, no amount of fiber “is going to overcome the issue” that they are full of sugar or salt, Corbin said. Concerns about medium aside, though, gut-health products elicited a shrug from her: Buying foods containing additional prebiotic fiber is a “reasonable approach,” so long as they’re healthy to begin with. If probiotics make a patient feel “fantastic,” Freedberg said, “I’m not going to rock the boat.” Prebiotic and probiotic products may help to a degree, but don’t expect them to overhaul an unhealthy gut one soda at a time. All of the experts I spoke with said that people concerned about their gut health should eat a lot of fruits, vegetables, whole grains, and legumes, and cut out junk that won’t feed their microbiome. In other words, a basic healthy diet is more than enough to achieve good gut health.

    My dad’s gut-health mantra was apparently borrowed from Hippocrates, suggesting that people have been obsessing over the digestive system for thousands of years with the belief that it is the key to overall health. The draw of this idea is its simplicity: Proposing that the body’s many ills can be collapsed into a single mega-ailment makes treatment seem refreshingly uncomplicated compared with the medical interventions needed to address individual problems. That the proposed treatments are easy and self-administrable—sipping fibrous soda, popping bacteria-packed pills—adds to the appeal.

    But perhaps what is most compelling about the idea is that there is some truth to it. Lately, research on the microbiome has seen some promising advances. A large study published in 2022 showed significantly elevated levels of certain bacteria in people with depressive symptoms. Another study, co-authored by Corbin in 2023, was one of the first to show, in a human clinical trial, that a high-fiber diet shifts the microbiome in a way that could promote weight loss. This moment is especially confusing because we are finally beginning to understand the gut’s connections to the rest of the body, and how eating certain foods can soothe it. Much more is known about the gut than in the days of Hippocrates, but still far less than the gut influencers on social media would have you believe.

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    Yasmin Tayag

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

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

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

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

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

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


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

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

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

    For more on longevity, see related videos below.



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    Michael Greger M.D. FACLM

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

    The Safety of Fasting to Lose Weight  | NutritionFacts.org

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    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. 

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    Michael Greger M.D. FACLM

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  • Does Fasting Benefit Weight Loss?  | NutritionFacts.org

    Does Fasting Benefit Weight Loss?  | NutritionFacts.org

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    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. 

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    Michael Greger M.D. FACLM

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  • Any Pitfalls with Restricting Calories?  | NutritionFacts.org

    Any Pitfalls with Restricting Calories?  | NutritionFacts.org

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    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. 

     

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    Michael Greger M.D. FACLM

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  • Sugar and Gaining Weight  | NutritionFacts.org

    Sugar and Gaining Weight  | NutritionFacts.org

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    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.

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    Michael Greger M.D. FACLM

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  • How To Keep The Munchies From Ruining Your Diet

    How To Keep The Munchies From Ruining Your Diet

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    All you need is to lose the holiday 2 pounds and maybe a wee bit more – but are afraid your marijuana use will work against you.  Don’t worry – we have a plan for you!

    The average holiday weight gain can be up to 2 pounds, couple it with weight creep over the year and you have a fresh goal for the annual January diet.  But what about you marijuana use and the munchies. not all cannabis products increase hunger. That’s because not all cannabinoids activate the receptors that affect your appetite levels. Tetrahydrocannabinol (THC) is the primary cannabinoid that’s known to increase appetite. But THC is only 1 of more than 100 active chemicals found in cannabis. But if it does, here is how to keep the munchies from ruining your diet.

    Buy your favorite healthy snacks

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    RELATED: Link Between Cannabis And The Munchies Is More Complicated Than You Might Think

    While a lot of people aren’t fans of healthy snacks, they’re an efficient way of curbing the munchies, and there are actually a lot of good snacks out there. Make sure to sample a lot of different things, from flavored popcorn to nuts, to pickled veggies, which are surprisingly delicious to eat while on a munchie binge.

    Prepare snacks at home

    What You Should Know About Cholesterol, Marijuana, And CBD
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    If you have some cooking skills, you can prepare some simple and delicious snacks at home, like home baked chips, egg free cookie dough, or puddings. Check out some more ideas here.

    Eat before you smoke

    4 Changes In Our Eating Triggered By The Pandemic
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    RELATED: Is Legal Marijuana Creating More Junk Food Junkies?

    While this plan may backfire, resulting in double the amount of calories consumed, you can try to have a satisfying meal before you smoke. This will prevent your body from going crazy with the munchies, although be sure to engage your brain with something else, minimizing the odds of eating double your portions.

    Plan, plan, plan

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    Before the munchie moment, be sure to clean your house from temptations, throwing away anything that’s caloric and that you consider a weakness. Stock up on healthy items or schedule a cardio workout before your planned smoking session. While this requires some foresight, it’s the best way to ensure your diet stays on track and your munchies stay under control.

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    Maria Loreto

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