Fasting
As many lapsed dieters can attest, even modest calorie restriction can be hard to sustain. And not everyone who wants to be healthy and long-lived wants or needs to be stick thin.
Mark Mattson, a researcher at the National Institute on Aging in Bethesda, Maryland, thinks an alternate route may be through what he calls intermittent fasting. Health benefits in mice that eat only every other day are similar to those for mice that eat a calorie restricted diet—they live 30 percent longer, Mattson says. And, he adds, “We see vast improvements in variables that indicate risk of disease.”
The calorie intake of the mice is not restricted during the “on” days; they often ate twice as much on the days they weren’t fasting.
Mattson said an earlier study found that mice that fasted every other day had extended lifespans and the new experiment found the mice also did better in factors involved in diabetes and nerve damage in the brain similar to Alzheimer’s disease.
“We think what happens is going without food imposes a mild stress on cells and cells respond by increasing their ability to cope with more severe stress,” Mattson said. “It’s sort of analogous to physical effects of exercise on muscle cells.”
He said the researchers think this stress occurs throughout the body, and that may be the reason fasting seems to increase lifespan and the animals become more resistant to the diseases of aging.
The dieting (calorie restricted) mice consumed 40% less food than mice eating normally and lost nearly half their body weight (49 percent) in the experiment, while the fasting mice weighed only a little less than mice eating normally.
Mattson and colleagues plan to study how this kind of eating pattern affects humans. Mattson already knows that some people do make the switch to intermittent fasting, with apparently little pain. After publishing a report on the diet’s benefits in mice, Mattson received calls and emails from people who, for a variety of reasons, decided to try intermittent fasting.
Mattson’s objective is not weight loss (though the ad hoc fasters happily report pounds lost, as well as other health benefits including reduced allergy sensitivity and more energy). Nor is Mattson especially interested in extending life span. Instead, he wants to boost what he calls the human “healthspan” — the period of a life in which a person enjoys good health, even into the eighties or nineties.
Even though fasting studies on rats, mice and other animals are encouraging, don’t expect your doctor to recommend it. Even for short periods, fasting can be dangerous for people with some medical problems, and - actually - mice and men are different. So doctors won’t be making fasting a dietary recommendation until studies on humans produce the same results as the ones on rodents.
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Apparent Prolongation of the Life Span of Rats by Intermittent Fasting