When melatonin gets released at night, the hormone sends signals to your body that it’s time to start winding down. As a result, your body goes into “rest mode,” with a focus on repair and restoration—and daytime functions like digestion slow down. (That’s why experts say to avoid eating late at night, when your metabolism is naturally slower, if you can.)
When you take melatonin, you kick-start this rest-and-recover process. So if you take the sleep aid, say, right after eating, you could impinge on your digestion without even knowing it. “If you eat your dinner late, let’s say 7:30 p.m., and then you take your melatonin at 8 p.m., you may be quieting your metabolism a little bit,” says Romm. “You may not get as much digestive fire, and it may actually affect weight gain.”
Of course, there’s an easy fix here: Just space out the time between eating and taking your melatonin. “If that means you need to bump your dinner a little earlier or take your melatonin a little later, that seems to be the antidote,” Romm adds.