Age-Related Disease Risk Lowers with Restricted Calorie Diet, Monkey Study Reveals

A 25-year study on rhesus monkeys has revealed that a calorie-restricted diet is associated with a significant reduction in mortality and age-associated diseases in the primates.

Writing in the journal Nature Communications, a team of researchers reports the latest finding from one of two ongoing, long-term studies on the effects of calorie-restricted diets of nonhuman primates.

The research, performed at the Wisconsin National Primate Research Center in Madison, included 76 rhesus monkeys. When the primates were between 7 and 14 years old their daily caloric intake was reduced by as much as 30 percent. Another group of monkeys were allowed to eat as much as they liked.

The group that was allowed unlimited access to food ended up with nearly three times more likelihood of developing diseases and a threefold increase in risk of death, the researchers found.

"We think our study is important because it means the biology we have seen in lower organisms is germane to primates," said study founder Richard Weindruch, a professor of medicine at the School of Medicine and Public Health at University of Wisconsin-Madison. "We continue to believe that mechanisms that combat aging in caloric restriction will offer a lead into drugs or other treatments to slow the onset of disease and death."

Other studies on the effects of calorie restricted diets on monkeys, notably one from the National Institute of Aging, found no differences in survival rates in primates with an imposed calorie restriction versus those without one.

The UW researchers, however, point out that the NIA study used prescribed diets, whereas their study determined how much food monkeys wanted to eat, then cut that amount by 30 percent.

"At all the time points that have been published by NIA, their control monkeys weigh less than ours, and in most cases, significantly so," said project co-leader Ricki Colman, a senior scientist at the Wisconsin Primate Center.

Because of the time and cost of these long-term primate studies, they are unlikely to be repeated, so scientists are eager to share data in order to get the most science value out of the work.

"We are now working with the NIA scientists to perform a comprehensive analysis of all of our data, taking into consideration the differences in study design, genetics, time of origin and composition of the diet. It's possible that insights we could not get from the individual studies will emerge from this aggregate data," said Rozalyn Anderson, an assistant professor of geriatrics and corresponding author of the UW study.

Anderson added that the research is not a lifestyle recommendation intended to suggest that people go out and cut calories by 30 percent to slow the diseases of aging.

"We are not studying it so people can go out and do it, but to delve into the underlying causes of age-related disease susceptibility," she said.

However, the data gained from studying the long-term benefits of caloric restriction in monkeys could lead to valuable insights into human health.

According to Weindruch: "The basic biology of caloric restriction in rodents, worms, flies and yeast seems to carry over to primates, so we have a real opportunity to dissect that mechanism, look at how we can work with that basic biology, and benefit all those human primates who are so closely related to our rhesus monkeys."