Jon Gertner's article in Sunday's New York Times, "The Calorie-Restriction Experiment," makes what seems a good case for a 25% reduction in caloric intake before concluding that such a course of action is rather impractical for 99% of Americans. Julian Dibbell came to a similar conclusion a few years ago in New York magazine.
Yet nobody can explain the precise mechanism by which this works. Is it possible that the simple act of being hungry, which is one of the effects of caloric restriction, causes the body to improve its functioning?
Indeed, according to the National Academy of Sciences, recent studies on mice showed that “intermittent fasting resulted in beneficial effects that met or exceeded those of caloric restriction including reduced serum glucose and insulin levels and increased resistance of neurons in the brain to excitotoxic stress. Intermittent fasting therefore has beneficial effects . . . independent of caloric intake.”
I suggest that if the NIH were to do a controlled study on intermittent fasting similar to the one they're doing on caloric restriction--let one group of people eat what they want on most days, but have them fast on Mondays and Thursdays; let another group of people eat what they want every day, but only between 1 p.m. and 8 p.m.; and let a third group be a control group, eating their normal diet--the health benefits of intermittent fasting might be found to be just as high as those for caloric restriction diets.
Gertner, relying on an interview with Dr. Luigi Fontana, writes, "The effects of calorie restriction may simply be an evolutionary legacy, 'a metabolic, hormonal and molecular adaptation' to a world of sparse resources. . . . By slowing aging and increasing resistance to disease during periods of food scarcity, the adaptive responses to fewer calories increased the odds that animals and humans that lived short lives might survive until they could reproduce." The same thing could be said about going hungry, which is a much more natural state than artificially restricting calories.
After all, practically every religion known to man has, until recently, prescribed fasting. Buddhists refrain from eating after noon on Uposatha days, which occur four to six times per lunar month. Catholics fast on Ash Wednesday and Good Friday, and used to fast more often before the 1950s. Mormons fast on the first Sunday of each month. Hindus fast at least once a week, depending on their local customs. Muslims fast from dawn to dusk during the month of Ramadan. Jews have two major (25-hour) fast days, Yom Kippur and Tisha b’Av, and four minor (dawn-to-dusk) ones. Almost all native American religions prescribe fasting of some sort. Fasting is almost universally perceived as conducive to spirituality, gratitude, charity, and atonement. It relieves stress and develops self-control.Hunger is an everday fact of life for the large majority of humans, and always has been. In most animals, hunger increases activity and movement; and being hungry certainly makes food taste better. For those of us who are lucky enough to live where food is plentiful, are our bodies evolutionarily well-equipped to handle the almost constant level of satiety that results from our ability to easily relieve hunger? Perhaps not. Caloric restriction is one way of getting the human body back to the way it was meant to be, but it involves weighing and measuring all your food, which is not exactly nature's course. Going hungry might be more natural, more efficient, and easier to do, simply by rescheduling when and how often one eats.