Not shoveling loads of food into your mouth is a guaranteed way to keep pounds off—but can limiting calories also keep you alive longer? Multiple studies over the past few years have hinted that it might.

But it took a monkey race to finally get to the bottom of it.

For years, researchers at the University of Wisconsin-Madison (UWM) and the National Institute on Aging (NIA) conducted dueling experiments on monkeys to attempt to come up with a definitive answer.

For example: In 2009, the Wisconsin team announced the results of a 20-year study that found that monkeys whose calories were cut by 30% experienced less cancer, heart disease, and insulin resistance—and, in turn lived almost twice as long. Not to be outdone, in 2012 the NIA folks threw their own monkey wrench into the works (sorry, bad pun) by proclaiming that, while a 30% calorie cut improved their primates’ health, it didn’t do squat to extend their lives.

Ultimately, facing a veritable jungle (sorry again) of conflicting data, the two sets of researchers decided to pool their resources to figure out who was right. In 2016 they teamed up and pored over both sets of data on almost 200 research monkeys, and came to this conclusion: Yes, eating less food increased their lifespan, but only: 1) if they started restricting their intake at an older age—best was post-adolescence; and 2) if they consumed whole, not processed foods. (Not to rub it in, but that means that UMW beat NIA’s ass, right? Just sayin’.)

So: What exactly would constitute “less food” in human terms?

Researchers are hesitant to specify, but calorie-restriction proponents like CR Society International recommend a drop of around 20%. Anything more than that, and—unless malnutrition is what you’re going for—you should check with your doctor first. In fact, check with a doc either way—better safe than sorry.

A final note: The typical lifespan of monkeys is 25 years, yet, amazingly, some of the original study monkeys are still alive—one even broke the longevity record at the ripe old age of 43. Compare that with a typical American guy’s lifespan of 79 years, and it could theoretically mean that, under the right calorie-deprived circumstances, you could live to around 135…and be hungry every single minute of it.