Prolonged fasting might do a body good. University of Southern California researchers found that occasionally skipping food for 2 to 4 days put humans and mice on the path to a healthier immune system.

Valter Longo, one of the team’s researchers, explained to The Daily Beast that a “mimicking” fast diet of 750-1050 calories per day for at least 4 or 5 days is sufficient to kick the body in a regenerative state. “Any fasting is better than nothing,” he said, “ [but] 4 to 5 days of fasting are necessary to maximize it’s effects, but they must be done under medical supervision and preferably in a clinic.”