Controlling calories and getting as much physical activity as possible should still be the top of everyone's list if you're looking to manage weight, but this researcher shows there are other things to consider as well.
The analysis focused on data on sleep, light exposure and weight gain during the study, but not on breast cancer.
The results suggest that cutting off lights at bedtime could reduce women's chances of becoming obese.
The study identifies an association between nighttime light exposure and weight gain, but can't directly prove the former causes the latter - the researchers acknowledge that some other factor could account for the link.
For the study, Park's team relied on self-reported data from almost 44 000 women, aged 35 to 74. The participants, aged 35-74 years, had no history of cancer or cardiovascular disease and were not shift workers, daytime sleepers, or pregnant when the study began.
The study researchers found that women who reported exposure to light at night while sleeping were more likely to gain weight and become obese over almost six years, compared with women who were not exposed to light at night. "This study highlights the importance of artificial light at night and gives women who sleep with lights or the television on a way to improve their health".
Although the new findings aren't conclusive, reducing your exposure to light and night may not be a bad idea.
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 findings add to a growing body of evidence suggesting that light at night may be bad for health.
"While sleeping with a small night light was not associated with putting on pounds, researchers found that women who slept with a room light or television on were 17 percent more likely to have gained approximately 11 pounds or more during the study's follow-up period". He is a postdoctoral fellow at the US National Institute of Environmental Health Sciences in Research Triangle Park, North Carolina.
Animal research and smaller studies in humans have linked prolonged light exposure with weight gain. "It seems reasonable to advise people not to sleep with lights on", Park and Sandler said.
Getting enough quality sleep every night is a tip at the top of any healthy living checklist, and lack of sleep has indeed been associated with a variety of conditions including obesity.
Poor sleep as a standalone factor has been proven to be associated with obesity and weight gain, but Dale Sandler, Ph.D. and a co-author of the research, said, "it does not explain the associations between artificial light exposure during sleep and weight gain".