Calorie restriction can help animals live longer. What about humans?

But the full picture is not so simple. Weight loss isn’t always healthy and neither is restricting your calorie intake, especially if your BMI is low to begin with. Some scientists warn that, based on evidence in animals, it could negatively impact wound healing, metabolism and bone density. This week let’s take a closer look at the benefits—and risks—of caloric restriction.

Eating less can make animals live longer. This remarkable finding has been published in scientific journals for the last 100 years. It seems to work in almost every animal studied—everything from tiny nematode worms and fruit flies to mice, rats, and even monkeys. It can extend the lifespan of rodents by between 15% and 60%, depending on which study you look at.

The effect of caloric restriction is more reliable than the leading contenders for an “anti-aging” drug. Both rapamycin (an immunosuppressive drug used in organ transplants) and metformin (a diabetes drug) have been touted as potential longevity therapeutics. And both have been found to increase the lifespans of animals in some studies.

But when scientists looked at 167 published studies of those three interventions in research animals, they found that caloric restriction was the most “robust.” According to their research, published in the journal Aging Cell on Wednesday, the effect of rapamycin was somewhat comparable, but metformin was nowhere near as effective.

“That is a pity for the many people now taking off-label metformin for lifespan extension,” David Clancy, lecturer in biogerontology at Lancaster University, said in a statement. “Let’s hope it doesn’t have any or many adverse effects.” Still, for caloric restriction, so far so good.

At least it’s good news for lab animals. What about people? Also on Wednesday, another team of scientists published a separate review of research investigating the effects of caloric restriction and fasting on humans. That review assessed 99 clinical trials, involving over 6,500 adults. (As I said, caloric restriction has been an active area of research for a long time.)