The longevity diet’s premise is seductively simple: cutting your calorie intake well below your usual diet will add years to your life.
But new research shows the extreme, emaciating diet doesn’t increase lifespan in rhesus monkeys, the closest human relatives to try it in a rigorous, long-running study. While caveats remain, outside experts regarded the findings as definitive, particularly when combined with those from a similar study.
“If there’s a way to manipulate the human diet to let us live longer, we haven’t figured it out yet and it may not exist,” said biologist Steven Austad of the University of Texas Health Science Center.
Since 1934, research has shown that lab rats, mice, yeast, fruit flies and round worms fed 10 per cent to 40 per cent fewer calories than their free-eating peers lived some 30 per cent longer. In some studies, they lived twice as long.
The new study suggests a surprising disconnect between health and life-span. It found most of the 57 calorie-restricted monkeys had healthier hearts and immune systems and lower rates of diabetes, cancer or other ills than the 64 control monkeys. But there was no longevity payoff.
“You can argue that the calorie-restricted animals are healthier,” said Austad. “They have better cholesterol profiles, less muscle loss, less disease. But it didn’t translate into greater longevity.”
While initial results were promising, the study found the oldest animals in each group had the same incidence of tumours, heart disease and general deterioration. Moreover, it found health markers were often worse in monkeys that began calorie restriction as young adults than older ones, the opposite of what scientists expected.