It seems eating less may lead to the fountain of youth -- for monkeys at least.

New research has found that monkeys that eat 30 per cent fewer calories per day live longer and have lower rates of heart disease and some types of cancer compared to monkeys that eat a regular diet.

The University of Wisconsin-Madison study found that 80 per cent of the monkeys on the calorie-restricted diet were still alive at the end of the 20 year study period. Only 50 per cent of the monkeys who were allowed to eat what they wanted lived to the end of the study.

The researchers also found that the monkeys that ate less had half the rate of heart disease and some cancers, and no cases of diabetes, a disease that is common in monkeys who are permitted to eat freely.

"We have been able to show that caloric restriction can slow the aging process in a primate species," lead study author Richard Weindruch, a professor of medicine in the UW-Madison School of Medicine and Public Health, 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."

The findings are published in the journal, Science.

Calorie-restricted diets have already proven to extend the lifespan and delay age-related health problems in worms, flies and mice.

But this is the first study to demonstrate such health benefits in an animal that so closely resembles humans.

The researchers also reported that their subjects' brains were also better-preserved when they ate fewer calories.

They found that the regions of the brain responsible for motor control, memory and problem solving seemed to function better, for longer.

"Both motor speed and mental speed slow down with aging," UW-Madison neurologist Sterling Johnson said. "Those are the areas which we found to be better preserved."

The study was released the same day as separate research, which found that a drug used to prevent the rejection of organ transplants increased the lifespan of older mice.

The drug, rapamycin, extended the lifespan of female mice by 14 per cent and extended the lifespan of males by nine per cent.

However, the drug cannot work in humans because it suppresses the body's immune system.