Less time sleeping may mean more time sitting down—and more weight gained, according to a new study.

The research, published in Annals of Internal Medicine on Monday, found that getting just 90 minutes less sleep each night for six weeks led study participants to sit around more and gain weight.

This study included 95 people who typically slept seven or eight hours each night. After the six weeks of sleep deprivation, however, the participants had gained about a pound, on average, and their sedentary time had increased by an average of 17 minutes. Men and postmenopausal women became the most sedentary, spending an average of 30 extra minutes sitting each day.

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This isn’t the first time researchers have connected sleep to weight, and particularly to obesity. In fact, not getting enough shut-eye is linked to increased risk of cardiovascular disease and other health problems, and more sedentary people are also at higher risk for chronic diseases. But many previous studies exploring sleep and weight have been conducted in labs—meaning they often take place over just a few days—and have involved far more drastic reductions in sleep, such as allowing participants a mere four hours of sleep over three days.

Short sleep-restriction studies don’t reflect the effects of chronic behavior that leads to these issues, says Marie-Pierre St-Onge, the study’s senior author and a professor of nutritional medicine at Columbia University Irving Medical Center. She argues that a six-week experiment conducted outside the lab and involving milder sleep restrictions is a more accurate representation of the realities of chronic mild sleep deprivation, which roughly 30 percent of adults experience, according to the authors.

“It’s a more naturalistic experiment, it more closely aligns with what we see, and it provides a message that’s directly applicable to what people actually feel,” she says.

In separate studies involving the same participants, she and her team have found that a decrease in sleep can raise the risk of type 2 diabetes and heart problems among certain groups.

The study stands out because it shows that lack of sleep is both associated with excess weight and that it causes weight gain, says Jean-Philippe Chaput, a senior scientist at the Children’s Hospital of Eastern Ontario, who studies sleep health and obesity and was not involved in this research.

“It shows what we already know in a more robust study design,” Chaput says.

One pound of weight gain over six weeks may not seem like a lot, Chaput adds, but it could become more significant if participants kept the same habits for many more months or years.

St-Onge hopes to focus her future research on potential interventions and the positive impact of getting enough sleep, she says.

“It’s easy to say that if you restrict your sleep, you have bad health outcomes. But the goal in life is not to do something bad to see if it has bad outcomes,” she says. “The goal in life is to do something good and then determine if it has healthful outcomes. So I think we should do a lot more of that now that we know that short sleep is not good.”

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