Rhesus monkeys Canto, 27 and on a restricted diet, is pictured at the Wisconsin National Primate Research Center at the University of Wisconsin-Madison on 28 May 2009. The animal is among the oldest surviving subjects in a pioneering long-term study of the links between diet and aging in Rhesus macaque monkeys, which have an average life span of about 27 years in captivity. [Image © University of Wisconsin-Madison University Communications/Photo by Jeff Miller]
Rhesus monkeys now join the list of creatures—from yeast to rats—who live longer and better when they eat less. Previous research has shown that cutting calories by about 30% can blunt the aging process in several animals, but the decades-long rhesus study published in the 10 July 2009 issue of Science strongly demonstrates the effect in a close relative of humans.
Ricki Colman and Richard Weindruch began their study in 1989 at the Wisconsin National Primate Research Center, with adult monkeys between the ages of 7 and 14 years old. Half of the monkeys were allowed to eat as much as they liked, while the other half had their calorie intake reduced by 30% compared to their free-eating days.
Twenty years later, 37% of the monkeys who ate without restrictions had died of age-related causes such as cancer and heart disease, while only 13% of the monkeys on the calorie-controlled diet had died from the same causes. "There is a major effect of caloric restriction in increasing survival, if you look at deaths due to diseases of aging," Weindruch said.
Diseases such as diabetes, which are common among all-they-can-eat lab monkeys, were absent from the Wisconsin dieters, the researchers found. And the normal shrinking of some parts of the brain that occurs during aging seems to be significantly slowed in the calorie-restricted monkeys, said Sterling Johnson, a University of Wisconsin-Madison neuroscientist who participated in the Science study.
It's unclear whether we could cut the risk of dying from an age-related disease by dropping a similar percentage of calories from our own diets, according to the Science authors. But given the biological similarity between rhesus monkeys and humans, Colman and Weindruch suggest that moderate calorie-cutting—and avoiding drastic diets that lead to starvation or malnutrition—could have beneficial effects on human lifespan.