Sleeping with a light on could lead to weight gain in women

Phillip Cunningham
June 14, 2019

"Our findings. suggest that lowering exposure to [artificial night at light] while sleeping may be a useful intervention for obesity prevention", researchers said.

Researchers from the U.S. National Institute of Environmental Health Sciences (NIEHS) examined 43,722 women aged 35 to 74 years. Those who reported sleeping at night in a room with a television on or a light were more likely to gain at least 4.9 kgs over about five years than those who slept in darkness.

The researchers analysed health and lifestyle data on almost 44,000 USA women enrolled in an ongoing study seeking clues to causes of breast cancer.

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

Women, beware: Sleeping with a light on or the TV going in your bedroom could make you put on weight.

When controlling for other characteristics that may be associated with increased artificial light exposure at night, like age, race, having an older spouse or children in the house, socioeconomic status, calorie consumption and physical activity, the researchers' findings did not change.

Daily exposure to light and darkness helps maintain our 24-hour body clock, which regulates metabolism, sleep-promoting hormones, blood pressure, and other bodily functions.

The research paper published on Monday in the journal JAMA Internal Medicine is the first study of its kind to find an association between any exposure to television or light at night and gaining weight in women.

Scientists still aren't sure of the exact reason, similar results linking prolonged light exposure and weight gain have been found in animal research and smaller human studies.

One of the factors pointed to by researchers is that light could suppress the sleep hormone melatonin and disrupt our circadian rhythms, according to ABC News chief medical correspondent Dr. Jennifer Ashton.

People face an increased risk of obesity if they fall asleep with the television on, according to new research.

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 ideal biological sense".

"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".

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