Few things are more satisfying than sleeping late on weekends. But though the extra z’s may improve your mood, they do not appear to improve your health. Because a new study shows that so-called “recovery sleep” cannot reset the body’s metabolic clock…and may actually lead to some serious health issues.

“Sleep loss can impact a range of physiological systems. It can increase our risk for cardiovascular disease, it can cause weight gain, it can decrease insulin sensitivity, so it can increase our risk of diabetes….

Christopher Depner, an assistant professor in the department of integrative physiology at the University of Colorado, Boulder.

“And this can happen, depending on what you’re looking at, this can happen as quick as one or two nights of not getting enough sleep.”

A lot of us shut off the alarm on Saturday and Sunday. But we go right back to burning the candle at both ends once the workweek begins.

“So we were really interested in how this sort of cycle of insufficient sleep, weekend recovery sleep, insufficient sleep, can impact your risk of obesity and metabolic disease.”

Depner and his colleagues invited volunteers to a nine-day snooze-a-thon. One group was allowed to get a full night’s sleep. The next was kept to just five hours each night. And the third group went back and forth, restricted to five hours of shut-eye during the workweek, allowed as much sleep as they wanted over the weekend, and then back to five hours for the last couple days.

The results?

“Well, the key findings from this study show that when we maintain insufficient short sleep schedules during a typical work or school week, we find that this leads people to eat more than they need and this leads to weight gain.”

Ken Wright, professor of integrative physiology at U.C. Boulder. He’s the senior author of the study, which appears in the journal Current Biology. [Christopher M. Depner et al., Ad libitum Weekend Recovery Sleep Fails to Prevent Metabolic Dysregulation during a Repeating Pattern of Insufficient Sleep and Weekend Recovery Sleep]

So it seems a loss of sleep leads to a spike in snacking. But even more surprising, sleeping in on the weekend doesn’t help—and even makes things worse.

“We found that after the weekend, when they went back to getting insufficient sleep during the work or school week, we found that their liver and their muscle insulin sensitivity or blood sugar regulation was reduced. And this is not something we had found in people who maintained chronic insufficient sleep schedules. So it’s possible that, yes, this is a worsening of the body’s ability to regulate blood sugar for those specific tissues after the weekend.”

So make a date with a pillow. And trade the sweets for sweet dreams.

—Karen Hopkin

[The above text is a transcript of this podcast.]