It’s a battle of two common fears: weight gain and darkness.

From a physical health perspective, weight gain can be dangerous if you pack on too many pounds, while living in darkness is fairly benign — especially when you’re asleep.

From a mental health perspective, many are afraid of the dark and rely on nightlights or television to illuminate their bedrooms to varying degrees while they sleep.

Not so fast.

A new study on women by the U.S. National Institute of Environmental Health Sciences and published by JAMA Internal Medicine has found a link between sleeping in lit rooms and weight gain, meaning the seemingly safe solution to one emotional fear actually could be triggering a physical one.

The report did not conclusively find a causal connection between artificial light and weight gain, so let’s take this finding with a grain of low-sodium salt.

There are plenty of conditions that tend to produce both weight gain — most likely through good old-fashion overeating and lack of exercise — and a preference for night light. For instance, loneliness, anxiety and depression each correlate with both behaviors. Plus, a lack of sleep has been linked to obesity for decades, so it’s something of a chicken-or-egg scenario.

For instance, loneliness, anxiety and depression each correlate with both behaviors.

Still, the analysis looked at 43,772 women with a mean age of 55.4, and the correlation was marked. Those who slept in light were 17% more likely to gain at least 11 pounds over five years.

Interestingly, the length of sleep does not seem to be a factor, but the brightness of the light does, according to the study.

Researchers concluded that artificial light exposure should at least be part of the larger obesity conversation.

Could Light Watchers be joining Weight Watchers at the health food store? In this age of smart appliances and general health awareness, it wouldn’t be surprising if smart bulbs began popping up at Whole Foods this summer.  

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