Being exposed to enough bright light early in the day may help you maintain your weight, according to a new study.
In the study, participants who were normally exposed to at least 500 lux of light (about the brightest level you'd find in homes and offices) starting at 8 a.m. had lower body mass indexes (BMIs) than those who usually got that much light exposure later in the day, the researchers found.
On average, for every hour that passed after 8 a.m. before a person was exposed to 500 lux, his or her BMI increased by 1.28 BMI unit, which translates to about 5 to 10 lbs., depending on a person's height, according to the study published today (April 2) in the journal PLOS ONE.
"Getting more light in the day was associated with a lower BMI," said study author Dr. Phyllis Zee, a professor of neurology at the Northwestern University Feinberg School of Medicine in Chicago.
"It is not just the amount of light that you get; it is really when in the day you get the majority of your light exposure" that seems to help regulate weight, Zee told Live Science. [Lose Weight Smartly: 7 Little-Known Tricks that Shave Pounds]
The study included 54 people with normal BMIs, whose median age was 30 years. The researchers examined the participants' exposure to light and other variables that may affect weight, such as their calorie intake, activity level and sleep patterns. Even when the research team adjusted for those other variables, exposure to light still affected people's BMIs.
"We can say that this [exposure to light] is an independent predictor of body mass index," Zee said.
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