Home Ernährung Das intermittierende Fasten am zweiten Tag auf die Probe stellen

Das intermittierende Fasten am zweiten Tag auf die Probe stellen

von NFI Redaktion

Preventing eating every other day slows down the metabolism that comes with weight loss, or does it improve compliance with constant, daily calorie restriction? What if, instead of reducing calories every day, you ate as much as you wanted every other day, or only for a few hours a day? What if you fasted for two days a week or five days a month? These are all examples of intermittent fasting regimens, as mentioned below and at 0:10 in my video Intermittent Fasting on Trial, and maybe we are even built for it. Three meals a day might be a relatively new behavior for our species. „For millennia, our ancestors couldn’t eat three meals a day. They ate much less frequently, often having only one large meal a day or going several days without food.“ Intermittent fasting is often portrayed as a way to stress the body – in a positive way. In biology, there is a concept called hormesis, which can be thought of as the principle of „what doesn’t kill you makes you stronger.“ Exercise is the classic example: you stress the heart and muscles and are healthier as long as there is enough recovery time. Is this the case with intermittent fasting? Mark Twain thought so: „A small hunger can do more for the average sick person than the best medicines and the best doctors.“ I don’t mean restricted eating, but complete abstinence from food for a day or two.“ But Twain also said, „Many a small thing has been made great by the right kind of advertising.“ Is the enthusiasm for intermittent fasting just a fad? Many diet fads have their roots in „legitimate science,“ but over time, facts can be distorted, benefits exaggerated, and risks downplayed. In other words, „Science gets overshadowed by marketing.“ At the same time, you don’t want to dismiss a potential benefit by immediately rejecting something based on the absurd claims of overzealous advocates. Religious fasting is the best-studied form of intermittent fasting, particularly Ramadan, a month-long period during which „Muslims fast from sunrise until sunset.“ The effects are complicated by changes in sleep patterns and thirst. The same dehydration problem occurs on Yom Kippur, when devout Jews stop eating and drinking for about 25 hours. The best-studied form of intermittent fasting, focusing solely on food restriction, is alternate-day fasting, where one eats every other day and alternates with days of low or no calorie intake. In a fasted state, we burn about a 50:50 mix of carbohydrates and fat, but usually, our glycogen – our carbohydrate stores – run out within 12 to 36 hours after eating. At this point, our body has to switch to relying more on our fat reserves. This metabolic switch could explain why the fastest rate of fat breakdown and burning occurs during a three-day fast between the 18th and 24th hour of the 72 hours. The hope is to reap some of the benefits of a break in eating without the risks of longer fasting. One potential benefit of fasting every other day vs. chronic calorie restriction is that you take regular breaks because you are constantly hungry. But could people be so hungry on their fasting day that they turn it into a feast day the next day? Mice fed every other day do not lose weight. They eat only about twice as much food on one day as non-fasted mice eat on two days, but that’s not what happens with humans. Study participants were randomly fasted for a day and a half – from 8:00 PM to 8:00 AM on the second morning after starting. The 36-hour fast only resulted in people eating about 20% more on the day after breaking the fast compared to a control group that didn’t fast at all. This would lead to a large calorie deficit for fasted individuals, equivalent to almost a thousand calories per day. Slim men and women participated in this particular study, but similar results were also found in overweight or obese participants. Researchers generally reported only a compensatory increase in calorie intake of about 10 to 25% over baseline on non-fasting days, and this seems to be the case regardless of whether the fasting day was a true zero-calorie fast or a modified fast with several hundred calories, which can lead to better compliance. Some studies found that participants apparently ate the same or even less on days after a one-day mini-fast. Even within studies, great variability is reported. In a 24-hour fasting study, where people ate an early dinner and then ate a late dinner the next day after skipping breakfast and lunch, the degree of compensation for the second dinner ranged from 7 to 110 percent, as you can see in the graphic below and at 4:40 in my video. This means that some participants were already so hungry at dinner that they consumed more than 24 hours‘ worth of calories in a single meal. The researchers suggested that people might want to first try „trial fasts“ to see how much their hunger and subsequent calorie intake increase before considering an intermittent fasting regimen. However, hunger levels may change over time and diminish as your body gets used to the new normalcy. In an eight-week study where overweight participants were restricted to about 500 calories every other day, they reportedly felt little hunger on reduced calorie days after about two weeks. This undoubtedly helped them lose around a dozen pounds on average over the course of the study, but there was no control group for comparison. In a similar study with a control group, a group of „normal-weight“ people, which in average means overweight, were found to lose a similar amount of weight of about ten pounds over a period of 12 weeks. In these modified diets where people were prescribed 500 calories on their „fasting days,“ researchers found that it apparently doesn’t matter for weight loss whether these calories are spread out throughout the day or consumed in a single meal. Instead of prescribing a specific number of calories for „fasting days,“ two Iranian researchers came up with the brilliant idea of using unlimited above-ground vegetables. Starchy root vegetables are relatively calorie-dense compared to other types of vegetables. Above-ground vegetables include stem vegetables (like celery and rhubarb), flower vegetables (like cauliflower), leafy vegetables (like, well, leafy greens), and all the fruits we normally consider vegetables (like tomatoes, bell peppers, okra, eggplants, beans, summer squash, and zucchini). So instead of prescribing a specific number of calories for „fasting days,“ the researchers allowed participants to switch between their regular diet and an all-you-can-eat feast of above-ground vegetables (along with naturally calorie-free beverages, like green tea or black coffee) every other day. After eight weeks, participants lost an average of 13 pounds and two inches off their waist, as you can see below and at 6:59 in my video. The same variability observed for calorie compensation was also found for weight loss, as shown in the graph below and at 7:10 in my video. In a 12-month trial where participants were instructed to consume only a quarter of their calorie needs every other day, weight changes varied from a loss of about 37 pounds to a gain of about 8 pounds. The biggest difference between the low versus high weight loss groups seemed not to be how much they indulged on their regular diet days, but how well they were able to adhere to the calorie restriction on their fasting days. Overall, ten out of ten alternate-day fasting studies have shown a significant reduction in body fat. Small short-term studies show a decrease in body weight of about 4 to 8 percent after 3 to 12…

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