Few joys are quite so splendid as being up early enough to watch the sunrise. But could that early morning light really help you lose weight? Surprising new research suggests it might, according to NPR

A study by researchers at Northwestern University found that exposure to early morning light, whether pure sunlight or bright indoor lighting, is associated with leaner body weights. The results appear to be in line with a growing body of evidence that suggests that it is healthier to keep your sleeping habits in tune with the daily light-dark cycle of the sun.

For the study, researchers strapped 54 adults from the Chicago area with wrist monitors that keep track of their wearers' sleeping patterns and exposure to light. Participants were also asked to keep careful records of what they ate on a daily basis so researchers could keep track of caloric intake. The monitoring period lasted for a week.

"We found that the earlier this light exposure occurred during the day, the lower individuals' body mass index," said study author Kathryn Reid.

Thanks to the aforementioned wrist monitors and participants' records, researchers were able to control specifically for the effect that light exposure had on participants' BMI. Activity level, caloric intake, sleep timing, age and season were all accounted for and factored in. It turned out that those exposed to more than 500 lux of light had the strongest light-to-BMI correlation. By comparison, 500 lux is roughly the equivalent to bright indoor lighting, and outdoor light can range from 1,000 lux up into the hundreds of thousands.

Reid theorizes that light exposure probably plays a role in regulating metabolism, much in the same way that the level of light exposure can cue wakefulness or sleepiness. Animal studies performed on mice have shown a similar correlation between light exposure and BMI, so the findings were not terribly surprising.

Though the study confirms a correlation between early morning light exposure and body weight, researchers have not yet confirmed a causal connection. So there's not yet any reason to think that simply turning the lights on in the morning will trim the pounds. The connection might not be so straightforward, and more experimentation will be necessary to hash out what's really going on. 

Fixing your sleep patterns to better coincide with daily light cycles certainly couldn't hurt, though. Many studies have shown that light is an important cue in synchronizing our internal body clocks. In general, researchers suggest people should get more bright light between 8 a.m. and noon specifically. They think about 20 to 30 minutes of morning light is enough to affect BMI. 

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