A new study reveals this common bedtime behavior could lead to excess weight gain among women.

By Rachel Sylvester
Updated June 13, 2019

Guilty of hitting the sheets without first hitting the lights? A new study reveals that snoozing while exposed to artificial light could lead to unintended health consequences over time—mainly, weight gain among women.

Published in the JAMA Internal Medicine medical journal, the data stems from a 5-year-long study that monitored the sleep patterns of 43,722 women across the United States and Puerto Rico. Information on individual sleep habits was observed, including whether or not each woman slept with a source of artificial light determined as either a television or nightlight. Data was recorded between the years of 2003 and 2009, and during that time, each participant carefully tracked their BMI in conjunction with their bedtime behaviors.

When asked to self-report their own level of artificial light exposure, participants were asked to choose one of four possible options categorized as the following: no light, small nightlight in the room, light outside the room, and light or television in the room. After analyzing the resulting data, researchers determined that sleeping with a television or nightlight on in the room was associated with a BMI increase of at least 10% compared to those participants who were exposed to no artificial light while asleep. In fact, sleeping in the presence of artificial light was positively associated with a weight gain of 11 pounds over a five-year period.

Defined as one's body mass index, BMI is calculated using an individual's height and weight. A BMI range of 25.0-29.9 is categorized as overweight by the CDC, while a BMI of 30 and above is considered obese.

Because the data was self-reported by participants, more research is necessary to identify a definitive link between bedroom light exposure and increased weight gain over time. Warnings of artificial light exposure and its effects on our circadian rhythms have long been purported, and this survey may be the excuse you need to start taking your sleep routine a little more seriously.

Concerned you're not logging enough hours of shut-eye per night? Strive for your best night's sleep by cutting the lights, eliminating screen time, and reaching for the remote before nodding off.