In 1908, Linda Hazzard, an American with some training as a nurse, published "Fasting for the Cure of Disease," which claimed that minimal food was the route to recovery from a variety of illnesses, including cancer. Hazzard was jailed after one of her patients died of starvation. But what if she was, at least partly, right?
A new surge of interest in fasting suggests that it might indeed help people with cancer. It might also reduce the risk of developing cancer, guard against diabetes and heart disease, help control asthma and even stave off Parkinson's disease and dementia.
"We know from animal models," says Mark Mattson at the National Institute on Aging, "that if we start an intermittent fasting diet at what would be the equivalent of middle age in people, we can delay the onset of Alzheimer's and Parkinson's."
Until recently, most studies linking diet with health and longevity focused on calorie restriction. They have had some impressive results, with the life span of various lab animals lengthened by up to 50 percent after their caloric intake was cut in half. But these effects do not seem to extend to primates. A 23-year study of macaques found that although calorie restriction delayed the onset of age-related diseases, it had no impact on life span. So other factors, such as genetics, may be more important for human longevity.
That's bad news for anyone who has gone hungry for decades in the hope of living longer, but the finding has not deterred researchers who study fasting. They point out that although fasting obviously involves cutting calories — at least on specific days — it brings about biochemical and physiological changes that daily dieting does not. Besides, calorie restriction may leave people susceptible to infections and biological stress, whereas fasting, done properly, should not.