Caloric restriction reduces mortality of rhesus macaques, a paper in Nature Communications reports this week. These results contrast with those of a previous study, in which caloric restriction had no effect on the lifespan of monkeys, however the authors outline that differences in feeding protocols and body weight of monkeys could account for these two seemingly contradictory findings.
Caloric restriction without malnutrition extends the lifespan of numerous organisms - from worms to mice - but whether it works in monkeys is controversial. Building on results from a long-running monkey experiment, Rozalyn Anderson and colleagues show a reduction of all-cause mortality, and not just age-related mortality, in response to caloric restriction. From this, they conclude that their data indicates that the benefits of calorific restriction on aging are conserved in primates.
As this finding is in contrast to those of a similar study published in 2012 in which caloric restriction had no effect on monkey lifespan, the team carried out a weight comparison of monkeys from both studies in order to investigate whether this could account for differences in findings. They conclude that the ‘control’ animals in the 2012 study were underweight, compared to national standards, and may have effectively been undergoing modest caloric restriction during the study. This could explain why additional caloric restriction in the intervention group had little or no additional beneficial effects. The reduction in weight of the ‘control’ animals, which may have led to the lack of beneficial effects of caloric restriction, may also be related to the different diets used in the two studies - whereas the food used in the 2012 study mimicked a comparatively healthy diet, the monkeys in the current study received a diet that contained more sugar and is more reminiscent of human feeding habits.