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One out of three U.S. adults say they get less than the seven hours a night of sleep experts recommend. If you’re among them, that can spell trouble for your health.

“In most laboratory studies where people have free access to food, those who sleep less eat more and tend to gain weight,” says Christopher Depner, assistant professor of health and kinesiology at the University of Utah.

For example, among 225 volunteers, those who were randomly assigned to sleep for no more than four hours a night for five nights in a row gained two pounds, while those who slept up to 10 hours a night gained nothing.

Unhealthy weight gain isn’t the only downside to insufficient sleep

“Laboratory controlled trials consistently show a reduction in insulin sensitivity when sleep is restricted,” notes Depner. Insulin sensitivity even fell in sleep-restricted healthy young men who weren’t allowed to overeat.

A drop in insulin sensitivity means that your body’s insulin is less able to move blood sugar into cells. Once your insulin loses enough of its punch, blood sugar rises and you’ve got type 2 diabetes.

“Our insulin sensitivity tests can detect changes that you won’t see if you go to a doctor,” says Depner. “A rise in fasting blood sugar might tip off a clinician that you have prediabetes. But that’s going to happen much further down the road.”

Does catching up on sleep over the weekend help?

Depner’s study asked a key question: “Most people try to catch up on lost sleep on the weekend, so we wanted to see if weekend recovery sleep had any benefits for metabolic health.”

His team randomly assigned 36 lean young men and women to one of three groups.

“One group had a simulated workweek of insufficient sleep,” explains Depner. “On Monday through Friday, we restricted them to five hours of sleep per night. Then they got a simulated weekend where they could sleep as much as they wanted. And then they went back to insufficient sleep for two days.”

Another group was allowed to sleep for only five hours a night for all nine nights, while the third group was allowed to sleep for up to nine hours a night.

What happened to the weekend-sleep group

“Weekend recovery sleep didn’t prevent weight gain or impaired insulin sensitivity,” says Depner.

“If you continually cycle back and forth between insufficient sleep during the workweek and recovery sleep on the weekend, that’s not going to protect you from the risk of weight gain and type 2 diabetes.”

“So the best advice is to try to get adequate sleep during the workweek.”

Few studies have been done on older people, notes Depner. “We don’t know what would happen if we were to look at people who were older, prediabetic, overweight, or who had other risk factors for type 2 diabetes.”

Looking for tips on how to get enough sleep?

Start with our interview with an expert on sleep disorders.

Photo: Daniel Rodriguez/