Running on empty: the pros and cons of fasting
Fasting restricts calories and may benefit your body. Is it a safe way to lose weight?
The number of obese Americans is now greater than the number who are merely overweight, according to government figures released last month. It’s as if once we taste food, we can’t stop until we’ve gorged ourselves.
Called intermittent fasting, this rather stark approach to weight control appears to be supported by science, not to mention various religious and cultural practices around the globe. The practice is a way to become more circumspect about food, its adherents say. But it also seems to yield the benefits of calorie restriction, which may ultimately reduce the risk of some diseases and even extend life. Some fasters, in fact, ultimately switch from regular, if comparatively rare, periods of hunger to permanent deprivation. They limit calories all the time.
“There is something kind of magical about starvation,” says Dr. Marc Hellerstein, a professor of endocrinology, metabolism and nutrition at UC Berkeley, who studies fasting.
Adds Mark P. Mattson, chief of the laboratory of neurosciences at the National Institute on Aging: “In normal health subjects, moderate fasting — maybe one day a week or cutting back on calories a couple of days a week — will have health benefits for most anybody.” Mattson is among the leading researchers on the effects of calorie restriction and the brain.
Not all nutrition professionals see the merits of fasting. Some think of it as a recipe for disaster, setting up a person for binge eating and metabolic confusion.
Ruth Frechman, a registered dietitian in Burbank and spokeswoman for the American Dietetic Assn., says she frequently sees such extreme strategies backfire. “You’re hungry, fatigued, irritable. Fasting is not very comfortable. People try to cut back one day and the next day they’re starving and they overeat.”
Researchers who study fasting and caloric restriction, however, say the body’s hunger cycle ultimately adjusts.
And from a biological standpoint, they say, fasting can be helpful whether someone is overweight or normal weight.