Women could gain weight by sleeping with TV on, study claims

Henrietta Brewer
June 12, 2019

The research showed that women who slept with a television or other light on in the same room at night were 17 percent more likely to have gained 11 pounds or more over the five-year follow-up period than those who slept with a small night light.

Sleeping with a television or light on in the room may be a risk factor for gaining weight or developing obesity, according to scientists at the National Institutes of Health.

The study involved nearly 44,000 USA women aged from their thirties to their seventies.

Among the women, the researchers found that sleeping with a television or light on in the room was associated with gaining five kilograms or more, a BMI increase of at least 10%, and a higher risk of being overweight or obese, compared with being exposed to no artificial light during sleep.

"Humans are genetically adapted to a natural environment consisting of sunlight during the day and darkness at night", Chandra Jackson, Ph.D., and the study's co-author said.

At their first check-in, the women were asked to report on their light exposure while they slept - whether they kept lights on in their rooms or in other rooms, whether light shone in through the windows, whether they slept with a TV on, and even from low-light sources such as clock radios. But new research points to another potential cause: how much light you're exposed to at night.

Lack of sleep has always been associated with obesity, but until now, the association between artificial light exposure while sleeping and weight gain has been unknown. On top of this, a shorter sleep simply means more time awake, and therefore more time to eat. "It seems reasonable to advise people not to sleep with lights on", Park and Sandler said. Women who slept with a mask on or reported no light while sleeping were classified as experiencing no artificial light exposure. People should also turn off all electronics in their bedroom and dim their alarm clocks to avoid the glare of any bright lights. Health officials recommend taking TVs and other tech devices out of your bedroom in order to support a healthy sleeping environment. However, their findings did not change when analyses controlled for characteristics that may be associated with exposure to light at night.

Professor Malcolm von Schantz, a professor of chronobiology at the University of Surrey in the United Kingdom who was not involved in the study, told the Science Media Centre that the study would have been stronger if the women had been wearing instruments that measured their activity as well as the exact amount of light they were exposed to, rather than depending on self-reports - "but the findings make flawless biological sense". "Exposure to artificial light at night may alter hormones and other biological processes in ways that raise the risk of health conditions like obesity".

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