It works with worms, rats, mice and monkeys. Reduce an animal's intake of calories by 30% and it will live 30% longer than those on an ordinary diet.
Now scientists want to know if the same severely restricted diet that has produced dramatic results in laboratory experiments in animals will work in humans. In September, the National Institute on Aging began scientific trials involving about 200 people at three locations in Louisiana, Massachusetts and Missouri. The volunteers are eating low-calorie diets to see if a significant reduction in calorie consumption will improve their health and enhance the likelihood of a longer life span. The institute's trials are noteworthy because the latest government figures show that a disturbing 61% of American adults are overweight, increasing their risk of heart attacks, strokes, diabetes and arthritis. Finding a diet that delivers maximum nutrition while sharply reducing calories -- and that people will stick with -- is a key goal of the research project.
Moreover, the public's appetite for remedies to slow the aging process is voracious. From memory pills to hormone shots and anti-wrinkle creams, the business of anti-aging is booming, but these products often make claims that are unsubstantiated by rigorous science. There is no pill or potion that has been proved to extend the human life span. The only scientifically demonstrated tool for increasing longevity is caloric restriction -- and it remains unproved in humans.
"We cannot guarantee the fountain of youth," said Dr. Charles Hollingsworth, the institute's chief of clinical trials in the geriatrics and gerontology program. But the payoff should be better health and the longer life that comes with a stronger immune system.
In the institute studies, some volunteers will try calorie restriction alone, while others will combine fewer calories with an exercise regimen. The scientists want to know if independent, impulsive human beings can get the same results with a highly disciplined diet as do laboratory animals who have no choice in the matter. The results of those on the special diet will be compared to a control group of similar people who are not changing their dining habits.
Because the human life span is so much longer than that of laboratory rodents, researchers won't know for a generation or more whether the calorie-restricted diet actually helps humans live significantly longer. For now, the scientists hope that the result of the highly disciplined diet will be better health into advanced old age.
