Falling asleep with computer, television on could lead to weight gain - study

Bad news if you're a late night TV binger: that habit of falling asleep to the new season of Big Little Lies could be causing you to gain weight.

A new study out of the US shows that falling asleep with the television or lights on can disrupt the body's natural circadian rhythm, leading to weight gain.

Almost 44,000 women were studied over a five-year period by the National Institute of Environmental Health Sciences. The findings, published by Jama International Medicine this month, showed that those women who reported leaving lights on while they fell asleep gained up to 5kg, compared to those who fell asleep in total darkness.

The women, aged between 35 and 74, had no history of cancer or cardiovascular disease and weren't shift workers, daytime sleepers or pregnant at the study's start. Yet, compared to those not exposed to artificial light, the women studied were 22 percent more likely to become newly overweight and 33 percent more likely to become newly obese. 

The authors said this could be because a lack of sleep changes the hormones that regulate appetite. And of course, a shorter time sleeping simply means more time to eat food.

Professor Malcolm von Schantz, from the University of Surrey, told the Daily Mail the findings "make perfect biological sense".

"We know that light in the late evening will delay our body clocks. We know from experimental studies in people that light at night affects our metabolism in ways that are consistent with increased risk of metabolic syndrome," he added.

"What is novel with this paper is that it is a longitudinal study comparing the weight of the same individuals at baseline and more than five years later."