Sleep loss increases the levels of endocannabinoid 2-arachidonoylglycerol (2-AG), a chemical signal that enhances the pleasure of eating, according to a study published in the journal SLEEP on Feb. 29. The 2-AG levels explains why the lack of sleep makes people overeat.
“We found that sleep restriction boosts a signal that may increase the hedonic aspect of food intake, the pleasure and satisfaction gained from eating,” says Erin Hanlon, a research associate in endocrinology, diabetes, and metabolism at the University of Chicago. “Sleep restriction seems to augment the endocannabinoid system, the same system targeted by the active ingredient of marijuana, to enhance the desire for food intake.”
They studied 14 healthy men and women who were in their 20s. The participants spent the first four days sleeping on an average of 7.5 hours and then they spent the next set of four days sleeping on an average of 4.2 hours.
They ate the same meals three times daily. The researchers measured their ghrelin and leptin levels, which boosts the appetite and indicates fullness respectively. High ghrelin and low leptin levels have been associated with reduced sleep time and increased appetite.
When the participants slept normally, their 2-AG levels were low in the morning. Their 2-AG levels peaked after lunchtime. However, when the participants did not get enough sleep, their 2-AG levels increased up to 33 percent, peaked at 2 p.m. and remained high until 9 p.m.
The individuals felt hungrier after not having enough sleep, which became more obvious after the second meal of the day and when 2-AG levels were highest.
Additionally, restricted sleep also made the participants eat 50 percent more calories than they did when they got enough sleep. Apparently, they were still hungry even after meeting 90 percent of their daily caloric needs two hours before.
The effects of sleep loss on appetite were most prominent in the late afternoon and early evening. Hanlon notes that an hour of staying awake burns 17 calories and totals to 70 calories when the participants lose four hours of sleep. Nevertheless, they took in 300 more calories which made the calories burned useless. If they keep on doing this, they will inevitably gain weight because of overeating.
“This tells us that if you have a Snickers bar, and you’ve had enough sleep, you can control your natural response,” Hanlon asserts. “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.”