miércoles, 23 de marzo de 2016

Molecular ties between lack of sleep and weight gain | National Institutes of Health (NIH)

Molecular ties between lack of sleep and weight gain

At a Glance

Researchers found that sleep restriction altered endocannabinoid levels—chemical signals that affect appetite and the brain’s reward system.
The results may help explain the link between insufficient sleep and obesity.

Couple in bed, with woman sleeping and man watching television.

Researchers are beginning to understand why sleep restriction increases hunger and food intake.GeorgeRudy/iStock/Thinkstock

A poor night’s sleep can leave you feeling foggy and drowsy throughout the day. Sleep deprivation has also been associated with higher risks of weight gain and obesity in recent years.

A group led by Drs. Erin Hanlon and Eve Van Cauter at the University of Chicago wanted to better understand how sleep and weight gain interact biologically. They noticed that sleep deprivation has effects in the body similar to activation of the endocannabinoid (eCB) system, a key player in the brain’s regulation of appetite and energy levels. Perhaps most well-known for being activated by chemicals found in marijuana, the eCB system affects the brain’s motivation and reward circuits and can spark a desire for tasty foods.

The researchers enrolled 14 healthy, non-obese people—11 men and 3 women—who were 18 to 30 years old. The participants were placed on a fixed diet and allowed either a normal 8.5 hours of sleep or a restricted 4.5 hours of sleep for 4 consecutive days. All participants underwent both sleep conditions in a controlled clinical setting, with at least 4 weeks in between testing. For both conditions, the researchers collected blood samples from the participants beginning the afternoon following the second night. The study was supported in part by NIH’s National Center for Research Resources (NCRR) and National Heart, Lung, and Blood Institute (NHLBI). Results were published in the March 2016 issue of Sleep.

When sleep-deprived, participants had eCB levels in the afternoons that were both higher and lasted longer than when they’d had a full night’s rest. This occurred around the same time that they reported increases in hunger and appetite.

After dinner on the fourth night, the participants fasted until the next afternoon. They were then allowed to choose their own meals and snacks for the rest of the day. All food was prepared and served in the clinical setting. Under both sleep conditions, people consumed about 90% of their daily calories at their first meal. But when sleep-deprived, they consumed more and unhealthier snacks in between meals. This is when eCB levels were at their highest, suggesting that eCBs were driving hedonic, or pleasurable, eating.

Hanlon explains that if you see junk food and you've had enough sleep, you may be able to control some aspects of 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.”

The authors noted that though the results are based on a small sample size, they are consistent with evidence from other research. Additional studies are needed to look at how changes in eCB levels and timing are affected by other cues, such as the body’s internal clock or meal schedules.

—by Tianna Hicklin, Ph.D.

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miércoles, 23 de marzo de 2016