Cutting calories by 30% slows brain ageing in monkeys, study reveals

A long-term study has found that cutting calories by nearly a third slows brain ageing in rhesus monkeys. Researchers at Boston University and the National Institute on Aging tracked the animals for two decades, observing clear differences in brain health between those on restricted diets and those fed normally. The findings, published in Aging Cell, suggest that sustained calorie reduction may protect key brain functions as animals grow older.

The study began in the 1980s with 24 male and female rhesus monkeys, whose median age of 32.1 years roughly corresponds to 66 to 108 in human terms. Half of the group ate a standard balanced diet, while the other half received 30% fewer calories but maintained the same nutritional balance. Over 20 years, the team monitored the monkeys' health until post-mortem examinations revealed striking differences.

Monkeys on the reduced-calorie diet showed far less metabolic dysfunction and oxidative damage in their brains. Their glial cells—critical for supporting neurons—displayed fewer age-related problems, helping to preserve the myelin sheaths that protect nerve fibres. This improved connectivity and overall brain structure compared to the control group. Originally, the study aimed to see if fewer calories would extend the monkeys' lives, which it did. Rhesus monkeys in labs typically live into their late 30s, while wild ones average around 19 years. The results also align with ongoing human research, such as the CALERIE trial, which is examining how calorie restriction affects ageing biomarkers in people. However, no findings from CALERIE on human ageing have yet been published, and the study's duration remains undisclosed.

The research provides clear evidence that long-term calorie reduction can slow brain ageing in primates. By maintaining healthier glial cells and neuronal connections, the diet appeared to protect against typical age-related decline. These results may inform future studies on human ageing, though further data from trials like CALERIE will be needed to confirm similar effects in people.