There’s a growing recognition that inadequate sleep may contribute to overeating and, thus, to our massive obesity epidemic. Now there’s a prime suspect to help explain why that may be so.
It’s the endocannabinoids, man.
Dr. Erin C. Hanlon
You’ve heard of them. They’re like the cannabinoids in marijuana that make eating so pleasurable and trigger the "munchies," except these are natural appetite stimulants in the body that control the pleasurable aspects of eating. A study presented at the annual meeting of the Endocrine Society showed that nine healthy, lean, young adults had higher blood levels of the endocannabinoid molecule 2-arachidonoylglycerol (2-AG) after only 4.5 hours of sleep compared with a normal night’s sleep when they got 8.5 hours in bed.
Researchers controlled what the participants ate and did during 6 nights in a sleep lab, testing their blood levels every hour for 24 hours after the second night of sleep.
They randomized participants to the normal-sleep or partial-sleep-restriction groups and had them return a month later in a crossover design to spend another 6 nights in the sleep lab experiencing whichever sleep pattern they hadn’t been randomized to initially.
The results showed a circadian rhythm to endocannabinoid levels, with 2-AG peaking in the early afternoon in both groups but being significantly higher in the sleep-restriction group, reported Erin C. Hanlon, Ph.D. and her associates.
Previous studies of the relationship between sleep and endocannabinoids had looked at only single time points or narrower time intervals, she said. The current results extend findings from at least a dozen previous studies in the last 5 years on related topics. In three studies, researchers reported an association between shortened sleep duration and increased eating of snacks and high-energy foods, such as in this study: Am. J. Clin. Nutr. 2012;95:818-24. Two other studies showed that decreased sleep was associated with increased risk for obesity. And seven other carefully controlled laboratory studies found that sleep restriction impaired glucose metabolism, altered peripherally secreted hormones that modulate feeding behavior, and increased participants’ ratings of appetite and hunger, said Dr. Hanlon of the University of Chicago.
Is lack of sleep the only cause of the obesity epidemic? Of course not. But a quick look at national data suggests that it could be a major factor, if these preliminary studies are on to something.
According to the Centers for Disease Control and Prevention, 35% of nearly 75,000 U.S. adults in 12 states reported in 2009 that they get less than 7 hours of sleep in a typical 24-hour period. Want to guess how many Americans reported being overweight in 2012? That would be 36%, according to a Gallup poll, with another 26% saying that they’re obese.
And are endocannabinoids the only endogenous players that affect overeating? Unlikely. But the endocannabinoid system is a target for development of potential pharmaceutical treatments for obesity, Dr. Hanlon said. Someday soon, I suppose, you may be able to buy a pill to counteract the munchie effects of excessive endocannabinoids. Or, we could all just get a good night’s sleep.
Dr. Hanlon reported having no financial disclosures. Her research was funded by the National Institutes of Health, the Department of Defense, and the Medical College of Wisconsin.
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