Consuming fewer calories can lead to a longer, healthier life, according to scientists studying the effect of diet on ageing in monkeys.
During the 20-year study on a group of rhesus monkeys, they found that those on normal diets were three times more likely to develop an age-related disease such as cancer, diabetes, or cardiovascular disease than those on restricted diets.
Previous studies have shown ageing can be slowed in mammals by a calorie-restricted diet or exercise, but the primate study is likely to provide better insight into the potential effects on human beings.
The scientists also found evidence that the brain health of animals on a restricted diet was better, particularly the regions associated with motor skills, memory and problem-solving.
Richard Weindruch, a professor of medicine at the University of Wisconsin-Madison school of medicine and public health, said: "We have been able to show that calorific restriction can slow the ageing process in a primate species. We observed that calorific restriction reduced the risk of developing an age-related disease by a factor of three and increased survival."
By the end of the study half of the animals permitted to eat as much as they liked had died, while only 20% of the monkeys given a third less calories each day had died.
The incidence of cancer and cardiovascular disease of those on restricted diets was less than half of that seen in the control group. Diabetes or impaired glucose regulation, common in monkeys allowed to eat all they want, did not appear at all in the other group. The scientists, who published their findings in the journal Science, also found that a restricted diet appeared to have an effect on brain health.
Sterling Johnson, a neuroscientist and co-author of the report, said: "It seems to preserve the volume of the brain in some regions. Both motor speed and mental speed slow down with ageing. Those are the areas which we found to better preserved. We can't yet make the claim that a difference in diet is associated with functional change because those studies are still ongoing. What we know so far is that there are regional differences in brain mass that appear to be related to diet."
The study, funded by the National Institute on Aging, began in 1989 with a group of 30 monkeys, with a further 45 added in 1994. Today, 33 animals remain in the study: 13 on a normal diet, 20 restricted.
When allowed to feed freely the average calorie intake of the rhesus macaques was 640 calories, while those on the diet were allowed an average of 480 calories.
