A combined analysis of two long-running primate studies shows that caloric restriction can improve health and survival in rhesus monkeys, a paper published in Nature Communications reports. The finding clarifies the effects of caloric restriction in monkeys, which were debated due to seemingly contradictory results obtained in the individual studies.

Caloric restriction - a reduction in food intake without malnutrition - has been shown to increase the lifespan of model organisms, such as yeast, worms, flies and mice, but whether it also works in nonhuman primates or humans is less clear. Two long-running studies involving rhesus monkeys have yielded seemingly contradictory results: one concluded that caloric restriction increased lifespan in monkeys, the other found no impact on survival but suggested benefits on monkey health.

In the current paper, the two groups compare and reanalyse their data, establishing a consensus that caloric restriction can have beneficial effects on both health and survival in monkeys. The authors also provide potential explanations for the varying outcomes of the individual studies based on differences in study design, such as the age of animals when caloric restriction was initiated, diet composition or feeding practices. The analysis also suggests that moderate caloric restriction is effective but further reduction of food intake does not increase the benefit in monkeys.

The study does not provide conclusive evidence as to whether caloric restriction slows down biological ageing of monkeys, and the minimum degree of caloric restriction that confers maximal benefit on health and survival in rhesus monkeys remains to be established. Given that the health benefits of caloric restriction are conserved in monkeys, the authors suggest that caloric restriction could have similar benefits on human health.