Image copyright Thinkstock Image caption Can extreme calorie counting lead to a long, healthy life?

Extreme calorie counting boosts lifespan in monkeys, according to new research.

Until now, the rationale for following an ultra-low calorie diet to ward off ageing has been based on experiments in worms and mice.

Studies reported in Nature Communications found primates also benefited from the regime.

A nutritionist urged caution over severe calorie restriction in humans, saying more research was needed.

Perhaps Benjamin Franklin was right when he said, 'To lengthen thy life lessen thy meals' Dr Emma Williams, British Nutrition Foundation

Advocates of the Calorie Restriction (CR) diet claim that by severely restricting the number of calories they consume they will live longer, perhaps into their hundreds.

They cite a wealth of scientific evidence dating back more than 75 years.

Much of the research is based on experiments in animals such as mice and worms, with primate studies giving conflicting results.

Now, a US team has published new evidence showing CR also shows benefits in primates.

Less is more

"CR works to delay ageing in primate species," Dr Rozalyn Anderson of the department of medicine at the University of Wisconsin-Madison, told BBC News. "Our study data is consistent with that."

The study found CR boosted survival in a group of rhesus monkeys studied over the course of decades.

Image copyright Thinkstock Image caption Monkeys lived longer when their daily food intake was reduced by a quarter

And she said conflicting findings, from a previous study at a different institute, might be due to flaws in the control group.

But she said CR was a research tool not a lifestyle recommendation.

"The concept is to delve into the biology of ageing and try to understand what's the basis for increased risk for diseases as you get older and with advanced age," she said.

"It would be very difficult to implement CR in a long term way in humans."

Caution advised

A US study is currently looking at whether healthy humans live longer on less food.

The participants restrict calories by 25% over several years, existing mainly on a diet of vegetables, fruits (especially apples), and soups.

Dr Emma Williams, a nutrition scientist at the British Nutrition Foundation, said caution was advised until results from human trials were available.

"Perhaps Benjamin Franklin was right when he said, 'To lengthen thy life lessen thy meals,'" she said.

"However, as this research was based on studies in primates more research is needed regarding the precise role of calorie restriction in human life expectancy before any definitive conclusions can be made."