BETHESDA, Md., Aug. 29 (UPI) -- A diet of 30 percent fewer calories but the same nutrients of a standard diet did not extend life in rhesus monkeys, U.S. researcher say.
However, first author Julie A. Mattison, head of the National Institute on Aging at the National Institutes of Health, said the reduction in calories did extend certain aspects of health.
The findings challenge those published in 2009 by the University of Wisconsin-Madison. The Wisconsin study followed two groups of rhesus monkeys for 20 years and found monkeys on a calorie-restricted diet lived longer than those on a standard diet.
The study, published in the journal Nature, found while calorie restriction had a beneficial effect on several measures of metabolic health and function in monkeys that were started on the special diet regimen during old age, it did not have the same positive outcome for monkeys started on calorie restriction at a young age. In the Wisconsin study, all the monkeys were young when started on calorie restriction.
"These results suggest the complexity of how calorie restriction may work in the body," Dr. Richard J. Hodes, NIA director, said in a statement. "Calorie restriction's effects likely depend on a variety of factors, including environment, nutritional components and genetics."
Both studies reported similar beneficial health effects -- diabetes, arthritis, diverticulosis and cardiovascular problems were delayed in those that experienced calorie restriction.