By Joelle Smith
If you wake up feeling exhausted, you might want to blame your body—not your bed: People carrying extra pounds may sleep less soundly than normal weight people do, research presented at the Sleep 2016 conference suggests.
In the study, overweight people—those who have a body-mass index (BMI) of 25 to 30—spent significantly more of their night in rapid eye movement, or REM, sleep than normal weight individuals with a BMI less than 25 did.
And that can be a problem, since REM sleep is less restorative and restful than other cycles like slow wave sleep.
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The researchers also took body fat into account, so people with a high BMI due to lots of muscle—like how the chiseled Dwayne “The Rock” Johnson Is Technically Obese—likely wouldn’t face the same risk.
It may come down to your body’s goal of energy homeostasis, or the balance between the amount of calories you take in versus the amount you burn off, says study author Andrea M. Spaeth, Ph.D., a postdoctoral fellow at the University of Pennsylvania.
Your body burns more calories in REM sleep than in more restful stages, possibly because your brain may be more active then, says Spaeth.
If you’re overweight, your body may spend extra time in REM to try to work off some extra calories.
More research must be done to figure out exactly how much weight you’d have to lose in order to cut your time spent in REM, Spaeth says.
But slow-wave sleep—the most restful, restorative stage—has also been associated with lean muscle, meaning the more muscle you have, the more restful you may sleep.