A major study in monkeys has found that substantially cutting calories from the diet could slow the ageing process and increase life expectancy.
Researchers at the University of Wisconsin-Madison, the Wisconsin National Primate Research Center and the William S. Middleton Memorial Veterans Hospital have found that a nutritious but reduced-calorie diet blunts aging and significantly delays the onset of such age-related disorders as cancer, diabetes, cardiovascular disease and brain atrophy.
"We have been able to show that caloric restriction can slow the aging process in a primate species," says Richard Weindruch, a professor of medicine in the UW-Madison School of Medicine and Public Health who leads the National Institute on Aging-funded study. "We observed that caloric restriction reduced the risk of developing an age-related disease by a factor of three and increased survival."
During the 20-year course of the study, half of the animals permitted to eat freely have survived, while 80 percent of the monkeys given the same diet, but with 30 percent fewer calories, are still alive.
Begun in 1989 with a cohort of 30 monkeys to chart the health effects of the reduced-calorie diet, the study expanded in 1994 with the addition of 46 more rhesus macaques. All of the animals in the study were enrolled as adults at ages ranging from 7 to 14 years.
Today, 33 animals remain in the study. Of those, 13 are given free rein at the dinner table, and 20 are on a calorie-restricted diet. Rhesus macaques have an average life span of about 27 years in captivity. The oldest animal currently in the study is 29 years.
Weindruch notes that in terms of overall animal health, the restricted diet leads to longer lifespan and improved quality of life in old age.
"There is a major effect of caloric restriction in increasing survival if you look at deaths due to the diseases of aging," he said.
The study has been published in the journal Science.