Artificial light at night may lead to weight gain

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If you leave lights shining or keep the television on while you sleep, it could affect your waistline, according to a study published online June 10 by JAMA Internal Medicine. The study found an association between exposure to artificial light during sleep and weight gain in women.

The research team looked at questionnaires completed by more than 40,000 women, which asked, among other things, whether the women slept with lights on nearby or in the same room. The researchers also recorded the women's height, body mass index (a measure of weight in relation to height), and waist size at the time they entered the study and then five years later. They found that women who slept with a light or television on in the room were 17% more likely to have gained 11 pounds or more during the course of the study. They did not find a similar effect when women used a small night light or had a light on outside the room that shone in. It's not clear why exposure to artificial light was linked with weight gain, but researchers speculated that it might affect sleep quality.