Keeping a lot of light on while you snooze — such as from a television or bright nightlight — has been linked with an increased risk of weight gain and obesity.

Specifically, sleeping with a television or light on in the room was positively associated with gaining five kilograms, or 11 pounds, over a five-year period among women in a new study published in the medical journal JAMA Internal Medicine on Monday.

“There was a 17% chance of gaining the five kilograms — after we adjusted for confounding factors,” said Dale Sandler, a senior investigator at the National Institute of Environmental Health Sciences in North Carolina and senior author of the study.

In addition, there was a 22% chance of becoming?overweight?and a 33% chance of becoming obese, she added.

Obesity means having too much body fat and overweight means weighing too much, according to the US National Library of Medicine. Both overweight and obesity are based on your body mass index but “obese” generally means having a much higher BMI.

“We are in the middle of an obesity epidemic in the United States and the things that we usually think about for obesity prevention are hard for people to do — eat a better diet, get more exercise — and we don’t seem to be making a dent,” Sandler said. “If these study findings are true and if they can be replicated then it’s a very easy public health message to turn off the lights when you’re sleeping.”