For a 2011 study in The Annals of Internal Medicine, researchers had 10 overweight, middle-aged participants go on a moderate diet. For two weeks, half of the participants slept for eight and a half hours per night. The other half only got to sleep for five and a half hours. Both groups lost the same amount of weight — three pounds (1.4 kilograms) on average — but those who got more sleep lost more in the form of fat. Those who got less sleep also showed higher levels of ghrelin, a hunger hormone. Increased ghrelin can make you hungrier, boost fat retention, and reduce calorie burn.

Weirder still, a 2016 study in the journal Sleep found that sleep deprivation can increase the peaks of a chemical known as an endocannabinoid. If that word looks familiar, it's because it's related to the word cannabis. Endocannabinoids act on the same parts of the brain that marijuana does (ever heard of the munchies?).

The study found that lack of sleep affects the daily rhythm of an endocannabinoid called 2-AG, which "may increase the hedonic aspect of food intake," study author Erin Hanlon told NPR. That is to say, it makes eating more pleasurable. That may be great news for your mouth, but bad news for your waistline.