Does how much you eat affect how long you live?
It has been a long-held belief that a restricted diet prolongs life. But a newly published 23-year study of rhesus monkeys has thrown the debate wide open by showing that less food does not necessarily mean a longer life.
In the study, rhesus monkeys were given 30% fewer calories in a balanced diet compared with control animals over a 23-year period. It found that eating less can improve health by delaying the onset of diseases such as diabetes, cancer and cardiovascular disease, but overall found no increase in lifespan for the calorie-restricted animals. The results were no different for monkeys that were relatively young at the start of the study or in their teens.
The idea that eating less could slow the ageing process was sparked in the 1930s when researchers found that rats and mice given a restricted diet could live almost twice as long. And in 2009, a different study of rhesus monkeys also showed fewer calories could prolong life. The contrasting outcomes in the rhesus monkey studies could be due to different compositions of the monkey’s diets, the authors of both studies say. The 2009 study also allowed the control monkeys to eat as much as they like, which would likely result in poor health from overeating.
Very few experiments investigating the effect of a calorie-restricted diet have been conducted using primates, which live a lot longer than rodents and are therefore a better model for predicting the effect of diet in people. This latest research is important because it challenges a long-held belief about diet and ageing using a well controlled experiment. Such experiments would be impossible in humans as there would be so many other variables that could affect the results.