Monkey lesson: Eat less to live longer

Monkeys on a reduced-calorie diet live longer than those that can eat as much as they want, a fascinating research suggests.

The findings add to a thread of studies on how a restricted diet prolongs life in a range of species.

In the study, which has been running since 1989 at the Wisconsin National Primate Research Centre in Madison, 38 rhesus macaques that were allowed to eat whatever they wanted were nearly twice as likely to die at any age than were 38 monkeys whose calorie intakes were cut by 30 percent.

The same study reported in 2009 that calorie-restricted monkeys were less likely to die of age-related causes than control monkeys, but had similar overall mortality rates at all ages.

"We set out to test the hypothesis - would calorie restriction delay aging? And I think we've shown that it does," said Rozalyn Anderson, a biochemist at the University of Wisconsin who led the study.

Eating a very low-calorie diet has been shown to prolong the lives of mice, leading to speculation that such a diet triggers a biochemical pathway that promotes survival.

But what that pathway might be - and whether humans have it - has been a matter of hot debate.

Another 2012 study at the US National Institute on Aging (NIA) in Bethesda, Maryland, cast doubt on the idea, reporting that monkeys on low-calorie diets did not live longer than those that ate more food.

"Are we seeing health benefits? Yes, but I do not know that we are necessarily seeing survival benefits," said Julie Mattison, a physiologist at the NIA.

Two key factors - the composition of the diet and the feeding regimen - could account for the different results.

But according to Anderson, the new findings are good news. "I have no doubt the results will be relevant to how we are treating people in geriatric clinics 10 years from now," she emphasised in the study published in the journal Nature Communications.