If you didn’t get enough sleep last night, you’re more likely by afternoon to be hungry and reach for Oreos or Doritos.
A new study has linked lack of sleep to eating too much junk food and, consequently, weight gain, NBC News reported. The basic premise of this hypothesis is that when people lack sleep, junk food becomes more tempting thanks to the intervention of marijuana-like chemicals produced in the brain.
“We know that when people use marijuana, they overeat. And they tend to eat things that are yummy and rewarding,” said endocrinology researcher Erin Hanlon from the University of Chicago.
The researchers studied a brain chemical called 2-AG for short (its full name is endocannabinoid 2-arachidonoylglycerol), which is a lot like the chemical found in pot. In the brain, it affects pain, pleasure, and appetite.
The chemical 2-AG is produced by two cannabinoid receptors, called CB1 and CB2; these receptors are part of the body’s endocannabinoid (eCB) system, which controls feeding, appetite, and the balance of energy in the body, Medical Daily added. This system also plays a role in “runner’s high.”
Researchers aren’t completely sure how endocannabinoids link to appetite, but they think it simply activates our feeding system. Somehow, lack of sleep also affects two appetite hormones in our brain, called ghrelin and leptin, but again, these effects aren’t very well understood.
“When you activate the cannabinoid system you are exciting the reward system,” Hanlon said.
The new study found that when volunteers were sleep-deprived, levels of that 2-AG brain chemical was high sooner in the day and stayed active longer. At the same time, the volunteers reported being hungrier, and they over ate, mostly junk food.
The brave guinea pigs in this study were healthy people aged 18 to 36. They weren’t obese and told researchers they usually managed 7.5 to 8.5 hours a sleep every night. None of them had any sleep disorders.
There were two sleep experiments. In the first, volunteers got plenty of winks for four days — 8.5 hours per night. In the second, they suffered a lack of sleep for the same period of time, getting only 4.5 hours per night. During the day, they only lounged around in a private room in dim lighting. Three times a day, each person was fed identical meals. Afterward, their levels of endocannabinoids and appetite hormones were measured.
And here’s what researchers found: people who slept enough had low levels of 2-AG. In those with a significant lack of sleep, 2-AG spiked by 33 percent, peaked at 2 p.m., and never waned. Those same people said they were hungrier when those levels jumped, maybe because their appetite hormones were lower. These participants also munched on snacks with double the calories and fat — in other words, junk food. Those who were well rested didn’t.
Further, on the fourth sleep-deprived night, no one was allowed to eat until 3 p.m. and then they could stuff themselves to bursting with their favorite foods. Afterward, they could keep snacking till their heart’s content, and a second meal was served at 7:30 p.m.
Everybody ate too much at 3 p.m., gorging on 2,000 calories. But those with a lack of sleep ate another 1,000 calories afterward. And, you guessed it, they ate junk food. The well-rested overate, too, but by 600 calories.
More research is needed into how a lack of sleep is connected to chowing down on junk food. Scientists also don’t know how to manipulate the endocannabinoid system to prevent people from eating junk food when tired.
According to Hanlon, the connection between lack of sleep and overeating is likely very complicated, and the answer isn’t hidden in the function of one brain chemical.
“We know sleep restriction inhibits cognitive performance. It inhibits impulsivity. You are more driven to overeat. 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.”