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Starving yourself for decades may help you live longer and age more gracefully, according to a long-anticipated study on the effects of calorie-restricted diets.

The research found that monkeys who eat less have a longer lifespan and better quality of life in old age.

Although the study was conduct on primates, scientists say the findings likely apply to people, too, and could have profound implications for human health.

The study was able to show that by cutting the calorie intake of monkeys by 30 per cent over a 20-year period, they were less likely to die from heart disease, cancer and diabetes, and less likely to have brain atrophy, than monkeys who ate whatever they wanted.

“We have demonstrated that calorie restriction can slow aging in monkeys, a primate species,” said Richard Weindruch, a professor of medicine at the University of Wisconsin-Madison. “We're primates too, so that makes it more probable that the biological effects of a calorie-restricted diet will have the same impact on humans, and slow the aging process.”

A photo of the oldest dieting monkey shows a robust animal with sleek fur and sharp eyes, compared with his more frail non-dieting counterpart, who appears portly with a matted coat.

The calorie-restricted diet serves to reprogram metabolism in a way that slows aging, says Prof. Weindruch, who led the study with Ricki Colman, an associate scientist at the Wisconsin National Primate Research Center.

The dieting monkeys still get all the vitamins, minerals and other nutrients they need to stay healthy. They are fed pellets containing milk, protein, carbohydrates and fat, and also receive one daily treat, usually a piece of fresh fruit such as an apple or a pear.

Scientists have already confirmed the relationship between diet and aging in other life forms, including yeast, worms, flies and rodents. They have also studied small groups of humans who follow calorie-restricted diets and found they have better-functioning hearts.

“We did a pilot study on humans and the results look optimistic. Calorie restriction alters the expression of many genes and peripheral blood cells,” Prof. Weindruch said.

The monkey study, published Friday in Science, began in 1989 with a cohort of 30 normal-sized adult rhesus macaques housed at Wisconsin's primate centre. Five years later, 46 more macaques – who have an average life span of 27 years in captivity – were added.

Today, 33 are still alive, 20 of them on a restricted diet, and 13 who eat what they want. Eighty per cent of the monkeys on the calorie-restricted diet are still living, compared with just half of the non-dieters.

For dieters, the risk of developing an age-related disease, including tumours and heart disease, was reduced by a factor of three. Not one has developed diabetes. They have all retained muscle mass. And their brain health is markedly better, displaying greater working memories and problem-solving skills than the non-dieters.

Since humans have a longer lifespan than monkeys, it may not be possible to fully study the effects of calorie restriction in humans, but monkeys do offer a close approximation.

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.

Members of the Calorie Restriction Society, based in North Carolina, sharply reduce their food intake in the hope of lengthening their life span.

“Any degree of restriction beyond what you're currently eating will confer health benefits and will slow the aging process,” Brian Delaney, the society's president, told The Wall Street Journal. He didn't say how difficult it is for humans to eat less.

And it's impossible to know whether the dieting monkeys suffer from constant hunger pangs and crave bananas and berries all day long, or whether their appetites shrink.

“Obviously we can't ask the animals if they are hungry,” Dr. Colman said. “But we do notice more food-centred behaviour in the restricted animals.”

For example, they increase activity in anticipation of feeding time and eat all of their food immediately after they receive it. If monkeys get excited at feeding time, imagine how humans feel.