Keeping Your TV on at Night May Lead to Weight Gain

Light exposure during sleep linked to weight gain in women study

Light exposure during sleep linked to weight gain in women study

Women exposed to artificial light at night were more likely to gain weight and become obese or overweight over the next five years, according to a study of nearly 44,000 people.

Dozing off to late-night TV or sleeping with other lights on may mix up your metabolism and lead to weight gain and even obesity, provocative but preliminary USA research suggests.

"Exposure to artificial light at night may alter hormones and other biological processes in ways that raise the risk of health conditions like obesity".

Although the authors cautioned they could not definitely draw a causal link, they said their findings added to a growing body of evidence that supports sleeping in a dark room.

However, the researchers found only an association, and they can't prove that exposure to light at night directly causes weight gain or obesity.

"Humans are genetically adapted to a natural environment consisting of sunlight during the day and darkness at night", said study co-author Chandra Jackson, PhD, from the US National Institute of Environmental Health Sciences, in a statement. "It seems reasonable to advise people not to sleep with lights on", Park and Sandler said. The few studies that have been conducted in the general population have typically collected data at a single point in time, so researchers haven't been able to determine whether light at night is tied to weight gain over time.

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.

Among women who weren't obese at the study's, those who reported exposure to any light at night were about 20% more likely to become obese during the study, compared with those who didn't report exposure to light at night. In fact, the data from a five-year period shows that those who have a TV or other light source on while they sleep gained over 10 pounds during that timeframe.

The findings held even after the researchers took into account factors such as where participants lived (in an urban, suburban or rural area), their household income, their level of caffeine and alcohol consumption, and any experiences of depression or high stress.

The researchers, from the National Institute of Environmental Health Sciences in the United States, followed 43,722 women aged between 35 and 74 years old, over a period of at least five years.

Exactly how is uncertain but scientists think disruption in release of hormones related to sleep and appetite may be involved.