The new research was published in Science and traces its origins to 1989, when the study began with 30 adult monkeys. Another 46 monkeys were added in 1994.
Half the monkeys were fed a low-calorie diet, and the other half a standard diet. All were closely monitored, with researchers regularly measuring their body composition, blood chemistry and endocrine function, as well as heart and brain function. When monkeys died, they were necropsied and the causes of death established.
All the surviving monkeys are now at least 27 years old, the rhesus equivalent of old age. Those fed a calorically restricted diet have dramatically lower levels of cancer, diabetes, heart disease, brain atrophy and lean-muscle loss. Just five of the 38 restricted monkeys have died from age-related causes, compared to 14 of 38 in the control group.
“Now we know that it works in a species closely related to humans. We can probe at the mechanisms, and hopefully understand them well enough to modulate them in some other way,” said Colman.
Whether drugs that mimic caloric restriction will benefit humans remains to be seen, and side effects are yet to be determined. But researchers can at least contemplate the possibility of slowing aging.
“It used to be said that it’s not going to be possible to affect aging, because there are so many different factors involved,” said Holloszy. “That’s no longer true. There are studies showing that affecting just one pathway produces long increases in longevity.”