KELLY MCEVERS, HOST:
Most of us know this, right? When we don't get enough sleep, we tend to get hungry and sometimes eat too much. The link between inadequate sleep and increased body weight is well known. Now, as NPR's Allison Aubrey reports, a new study published in the journal Sleep explains why we tend to eat more when we're tired.
ALLISON AUBREY, BYLINE: You've probably heard of the munchies, right? When people smoke pot, their desire for food goes up and what they eat just seems yummier. Researchers at the University of Chicago wondered if a lack of sleep might lead to overeating by affecting the brain in a similar way, so they designed an experiment at the University's sleep lab. Researcher Erin Hanlon says they began by recruiting 14 healthy young adults.
ERIN HANLON: These were all people that were, quote, unquote, "normal sleepers," so all the people typically slept about eight hours a night.
AUBREY: The study was divided into two parts. For one session, they were allowed to sleep normally. For the other, they agreed to a crazy schedule. They went to bed at 1 a.m. and were woken up at 5:30, so they got just four-and-a-half hours of sleep. In both sessions, they were offered buffet-style meals and plenty of snacks.
HANLON: They were given way more food than they could ever eat.
AUBREY: And it turned out that when participants were sleep deprived, they ate.
HANLON: During the normal sleep condition, they ate about 600 calories of snacks. And in the sleep restriction condition, they ate almost a thousand calories and snacks.
AUBREY: That's a lot more.
HANLON: Yeah, it's a lot more.
AUBREY: Now, to try to figure out what was going on, the researchers took blood samples from each participant. They measured levels of a specific lipid in the bloodstream - an endocannabinoid, which is spelled like and sounds like cannabis. Our bodies make endocannabinoids, and they act on the same brain receptors as marijuana. What Hanlon and her team discovered is that when people missed out on sleep, the endocannabinoid levels peaked higher.
HANLON: So when you see an increased peak in endocannabinoid levels, people are saying they feel hungrier or their desire to eat is stronger.
AUBREY: So it really does look kind of like the munchies.
HANLON: Right, exactly.
AUBREY: Hanlon says endocannabinoids are certainly not the only influence here. When our circadian rhythms are thrown off, lots of factors alter our eating. But she says she hopes that her findings are a reminder to people of the importance of a good night's sleep. Allison Aubrey, NPR News.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.