A 20-year study of monkeys shows that a reduced-calorie diet pays off in less disease and longer life, U.S. researchers said on Thursday.

They said rhesus monkeys on a strict, reduced-calorie diet were three times less likely to die from age-related diseases like heart disease, cancer and diabetes over the study period than monkeys that ate as they liked.

“We have been able to show that caloric restriction can slow the aging process in a primate species,” Richard Weindruch of the University of Wisconsin in Madison, whose study appears in the journal Science, said in a statement.

“We observed that caloric restriction reduced the risk of developing an age-related disease by a factor of three and increased survival,” Weindruch said.

The study in primates reinforces similar findings in yeast, worms, flies and rodents, and suggests other primates - including humans - may benefit, too.

Since people live far longer than monkeys, it may never be possible to fully study the effects of calorie restriction in humans, but monkeys do offer a close approximation, the team said.

Most caloric restriction studies have found that a lifetime of deprivation is needed to achieve the longer-life benefits, and many research teams are working on ways to replicate the findings with drugs.

Researchers reported on Wednesday that the antibiotic rapamycin, sold by Wyeth under brand Rapamune to suppress the immune system in transplant patients, showed promise at slowing age-related disease in older mice, but it is not clear how it works.

And several teams are hoping to harness the age-defying benefits of red wine. GlaxoSmithKline last year spent $720 million to buy Sirtris Pharmaceuticals, which has developed a souped-up version of the red wine compound resveratrol that has been found to make mice live longer and stay healthier.

MONKEY ATE 30 PERCENT FEWER CALORIES

In the latest study, Weindruch and colleagues studied the effects of calorie restriction over two decades in a group of rhesus macaque monkeys.

Half of the monkeys were allowed to eat as they pleased, and the other half ate a carefully controlled diet that provided just two-thirds of the calories they would normally choose to eat.

The team found that half of the monkeys that were allowed to eat freely over the course of the 20-year study have survived, while 80 percent of the monkeys that ate 30 percent fewer calories over the same period are still alive.

While rhesus macaques have an average life span of about 27 years in captivity, the team said.

The animals that ate less had half the amount of heart disease and cancer, and there were no cases of diabetes in the low-calorie group.

Animals on a restricted diet also had more brain volume in some regions than the animals that ate freely, suggesting diet may affect brain health in aging as well.

SOURCE: Science, July 10, 2009.