Intermittent Fasting: The Meal-Skipping Fad
Image Description: An empty white plate with a tape measure around the bottom and a fork on the left and a knife on the right.
Intermittent fasting (IF) seems to be everywhere. It started like so many other diet fads spreading on social media and then jumping to commercial weight loss programs. Unlike most fads, IF made the leap to the New England Journal of Medicine and from there to medical media. Soon we were all hearing about the wonders of IF from our doctors at every visit.
Where did IF come from? IF is really nothing more than skipping meals. Since the 1950’s, the weight loss industry has been united in warning us off skipping meals. Diet books, programs, articles in Good Housekeeping magazine, brochures in doctor’s offices, all were unanimous that no matter what you did or what kind of radical unbalanced diet you tried, you should always eat three regular meals a day. Don’t skip or “You’ll get too hungry and end up eating more food and gaining weight.”
What changed? Like many fads, it started from a kernel of truth. Nutrition studies have now shown that everyone does not have to eat breakfast. Many people are not hungry in the morning, yet they force themselves to eat because they heard that breakfast is the most important meal of the day. It turns out many people can function just fine fasting until lunch if you dislike breakfast. On the other hand, if you wake up hungry in the morning there is no point in starving yourself simply to follow the anti-breakfast trend. The best approach may be intuitive eating –follow your body regarding whether to eat breakfast or not.
So it is true that breakfast-haters can skip. On the other end of the day, a bedtime snack might be avoided too, if only because it contributes to acid reflux at night. If you are too hungry to sleep at bedtime, it may mean you need to eat more at dinner time to carry you through the night. If you skip the bedtime snack, then you are not eating from dinner to lunch. Without any deliberate effort, you are following a plan of 8 hours of eating and 16 hours of fasting. This 8 on/16 off pattern may be the most popular IF scheme. There is no reason to set a timer and get the schedule just right. Intuitive eating should serve you fine.
The IF fad really took off when a long and very enthusiastic article was published in the New England Journal of Medicine(de Cabo & Mattson, 2019). Only a few small short term human trials could be cited. We have often seen these studies of a small number of enthusiastic volunteers. Such studies showed that eating on small serving plates, keeping a food diary, drinking water before meals or eating unappealing foods like rice cakes and bitter greens can yield weight loss. Larger studies covering longer test periods and tracking people who dropped out of the study always reveal the truth –that none of these diet gambits have any lasting effect on weight. History seems to be repeating itself with intermittant fasting.
The New England Journal of Medicine article also reviewed a great many experiments with lab rodents. Studies of lab rats and mice can be very informative and can lead to advances in medicine. However, it is important to replicate, as much as possible, the human condition. In 1984, as part of my doctoral thesis I reviewed more than 100 articles on IF in lab animals and in farm animals. These studies showed that IF had negative effects similar to the consequences of weight cycling, also called the yo-yo syndrome. For example, IF is a strategy for fattening cattle on a limited amount of feed, as might be found in emerging nations. IF creates beef marbled with fat, producing tender juicy steak.
Up until 1990 or thereabouts, lab animal studies used genetic models. Because body weight is strongly inherited in humans, genetic fatness in lab animals mirrors the human condition well. But around 1990 there was a wholesale shift to dietary models, almost entirely done in mice. Through years of painstaking study, it was found that mice will get fat if fed a very particular mix of shortening and sugar resembling cake frosting. Put in the wrong proportions, and the mice will not gain weight. Nearly every study you read about “obesity science” in the news concerns mice fed cake frosting. If you add any other food to the cake frosting diet, the mice will lose weight. If you take away the cake frosting for a few hours a day, the mice will lose weight. Almost anything you can think of, including putting in a running wheel in the case, will “cure the obesity”. This is why there are hundreds of headlines trumpeting “XYZ Cures Obesity”. It’s all about getting mice to cut down a little on all the cake frosting.
Studying mutant mice with genes that promote weight gain is very hard. If you try to starve genetically obese mice, they will break down their muscle and vital organs to preserve their fat. Only a few scientific papers were being published. But now, with the cake frosting method, a flood of scientific papers has erupted, which has allowed a flood of government research grants to flow from the National Institutes of Health. Almost anything can resemble a cure for obesity, including IF. The recent result is an endorsement from the New England Journal of Medicine.
The diet doctors and the diet spokespersons go on to claim a long list of health benefits and effortless weight loss from IF. The data are finally in 2020 and there is no advantage or benefit from skipping meals (Lowe et al., 2020). The TREAT trial compared dieters who were told to eat only between noon and 8pm with a control group told to eat at any time. Neither group lost weight and they finished within one half of a pound of each other. The IF group lost lean body mass relative to controls and there were no other medical changes. Nine of the IF group dropped out of the program within 12 weeks, versus only 2 in the control group. The dieters apparently found the regimen difficult and all they achieved was a loss of lean body mass with no loss of body fat.
Muslims fast during the daylight hours for the month of Ramadan, which amounts to an IF for a month, with a large meal at sunset another just before dawn. Is Ramadan fasting beneficial? A meta-analysis shows that average Muslim loses less than 3 pounds over the course of a month (Patterson & Sears, 2017), at least some of which is the result of dehydration. Remarkably, nearly all that weight is regained in just two weeks after the holiday of Eid at the end of Ramadan. Not surprisingly, blood sugar and cholesterol drop slightly during the religious observance. There is no evidence of lasting benefit once the month is over.
IF ultimately is just one more fad diet, despite its surprising embrace by the medical establishment. Like other fad diets, few people can stay on it and those that do have little or nothing to show for it.
###
de Cabo, R., & Mattson, M. P. (2019). Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine, 381(26), 2541-2551. doi:10.1056/NEJMra1905136
Lowe, D. A., Wu, N., Rohdin-Bibby, L., Moore, A. H., Kelly, N., Liu, Y. E., . . . Weiss, E. J. (2020). Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial. JAMA Intern Med. doi:10.1001/jamainternmed.2020.4153
Patterson, R. E., & Sears, D. D. (2017). Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition, 37, 371-393. doi:10.1146/annurev-nutr-071816-064634
