CHICAGO, March 1 (UPI) -- A chemical reaction in the brain causes people who don't get enough sleep to eat more -- specifically, to eat more junk food -- for reasons similar to getting the munchies after smoking pot, researchers say.
Researchers at the University of Chicago found endocannabinoid production in the brain increases with lack of sleep, increasing the the pleasure derived from eating sweets, candy, and other delicious but unhealthy foods.
Sleep deprivation can affect cognitive decision making and impulse control, suggesting people have a reduced ability to resist urges for the junk food they enjoy. The researchers also point out about one-third of Americans don't sleep enough and three-quarters are overweight.
The urge to overeat is complicated, they said, and sleep may play a larger role than previously thought.
"We know sleep restriction inhibits cognitive performance. It inhibits impulsivity. You are more driven to overeat," Erin Hanlon, a research associate at the University of Chicago, told NBC News. "If you have a Snickers bar, and you've had enough sleep, you can control your natural response. But if you're sleep-deprived, your hedonic drive for certain foods gets stronger, and your ability to resist them may be impaired so you are more likely to eat it. Do that again and again, and you pack on the pounds."
For the study, published in the journal Sleep, researchers recruited 14 healthy men and women to sleep in a lab for two four-night visits, one with normal 8.5-hour nights of sleep and the other with restricted 4.5-hour nights of sleep, measuring their hunger, appetite and food intake during the four-day stretches. Each day, they were given identical meals at 9 a.m., 2 p.m., and 7 p.m.
In addition to participants reporting they were more hungry and had a stronger desire to eat in the afternoon when they had less sleep, they also ate nearly twice as many snacks when given unlimited access.
The researchers found levels of endocannabinoid 2-arachidonolyglycerol, or 2-AG, was present in higher levels in the bodies of those with less sleep, and peaked somewhere around mid-afternoon -- when participants reported they were the most hungry.
"The large overarching message is sleep restriction and sleep deficiency have been associated with multiple deleterious outcomes, and it's important for us to realize that adequate sleep is an important aspect of maintaining good health," Hanlon told the Washington Post. "People who believe in the old adage 'I'll sleep when I'm dead' need to revisit their thinking."