Not getting enough sleep at night may make you want to eat too much the next afternoon. That’s the conclusion of a study that finds skimping on rest can trigger a response similar to the effect of smoking marijuana—namely the munchies.
Evidence has been accumulating in recent years that people who don’t get enough sleep are at higher risk of putting on extra weight. And while this nexus may not be a surprise to everyone, scientists are beginning to uncover the mechanisms that make it an unhappy reality.
“We know that marijuana causes individuals to overeat when they’re not hungry,” said Erin Hanlon, a research associate at the University of Chicago’s Sleep, Metabolism and Health Center. “Our findings suggest that sleep restrictions may be acting in the same manner and on the same system.”
Hanlon and her collaborators put 14 healthy adults—11 men and three women—through two separate four-day sessions in the sleep lab. In one of the sessions, they were allowed to sleep eight and a half hours per night. In another, they were restricted to four and a half hours per night. The participants didn’t leave the lab for the duration of each four-day session. “No naps were allowed,” according to the paper, published on Monday in the journal Sleep.
In both sessions, researchers strictly controlled what the subjects could eat for the first three days. On the fourth day, after fasting all morning, they were led to a buffet of food far in “excess of what they could eat,” Hanlon said. The spread included pizza, chicken, steak, burgers, as well as healthier options. The participants were also given unlimited snacks for the rest of the afternoon.
Regardless of how much they had slept, people ate a lot at each buffet—taking in most of the calories they needed for the day. The difference appeared during the post-lunch grazing: while people ate snacks whether they were rested or not, they were less able to resist extra helpings when they had only 4.5 hours of sleep, even though they’d largely met their daily caloric needs an hour or two before. Their gorging coincided with an increase in a chemical known as 2-AG, which acts on the endocannabinoid system—the same one that THC, the active ingredient in marijuana, affects.
Other studies have shown that missing sleep messes with hormones that affect appetite and feelings of satiety. More work needs to be done to show to what extent munchies induced by lack of sleep may be involved in weight gain. But the finding is consistent with other research linking short sleep to metabolic problems, said Frank Scheer, an associate professor at Harvard Medical School. (He wasn’t involved in the experiment but wrote a commentary on the research.)
Sleep is “not a standalone system—it integrates with food and exercise,” Scheer said. And untangling the role it plays in weight gain may be important to reversing the climb in obesity rates. “We’re all sleeping too short,” Scheer said. That may mean we’re all eating too much, as well.