Fasting Away Disease?

Your mother may have been wrong: skipping meals may be good for you. It has been known for years that sharply restricting the calorie intake of laboratory animals increases their life span. But a new study by researchers from the National Institute on Aging found that mice that fasted every other day, then were allowed to eat what they wanted on the intervening days, seemed more resistant to diabetes than did control mice or animals on calorie-restricted diets. They were also resistant to a condition similar to Alzheimer's disease.

Intermittent fasting is a much more palatable lifestyle than the continual self-denial of a highly calorie-restricted diet, says Judith S. Stern, Sc.D., vice president of the American Obesity Association. "You can almost have your cake and eat it too."

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Study author Mark Mattson, Ph.D., hypothesizes that intermittent fasting works because each fast is a mild stress. The animals respond by increasing production of substances known as stress-resistance proteins, which may make them more resistant to disease. In addition, the intermittently fasting mice produce more of a chemical called brain-derived neurotrophic factor (BDNF), which promotes learning, memory and the growth and survival of nerve cells. This BDNF appears to make the animals more resistant to a neurotoxin that produces brain damage similar to Alzheimer's disease, Mattson says.

The intermittently fasting animals' cells also become more adept at scavenging glucose from blood. That, says Mattson, is an antidiabetic effect, detectable on glucose tolerance tests.

Stern cautions that it will be years before researchers puzzle out what this means for humans. In the interim, healthy adults who decide to fast might not be at great risk, she says, but it may be difficult to achieve balanced nutrition or to avoid pigging out excessively on the feast days. Children should not be put on such a diet, she says. And she notes that some medications probably would not work properly under such a regimen. "If you have any chronic illness and decide to do this, you really ought to be in communication with your doctor."

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