EDMONDTON, Alberta — That maddening annual weight gain over the winter months may have less to do with the lack of physical activity you’re getting and more to do with the lack of sunlight you’re exposed to while you hunker down for warmth, according to a new study.

Researchers at the University of Alberta studied tissue samples from individuals who’d undergone tummy tucks and found that the fat cells lying directly below the skin shrink when exposed to the visible light from the sun. Senior author (and aptly-named) Peter Light, a professor of pharmacology at the school, says that the sunlight that humans can see — also known as blue light wavelengths — comes into contact with fat cells located beneath the skin, causing lipid droplets to shrink and leave the cell.

Sunlight through trees
All those sweets you ate over the holidays may not be the root of your weight gain. A new study finds that a lack of exposure to sunlight during the cold winter months causes the body to store more fat. (Photo by George Hiles on Unsplash)

“In other words, our cells don’t store as much fat,” explains Light in a news release.

That said, if sunlight is aiding in preventing weight gain when people are routinely enjoying time outside, then we’re more likely to pack on the pounds when we spend more time inside.

“If you flip our findings around, the insufficient sunlight exposure we get eight months of the year living in a northern climate may be promoting fat storage and contributing to the typical weight gain some of us have over winter,” says Light.

Still, researchers are quick to warn people from running out to catch the brief winter sun. Light and his team admit they don’t yet know the recommended light intensity and duration to cause the desired effects in the fat cells.

However, the breakthrough study could lead to new treatments for obesity and even diabetes in the future, including light-based treatments. “Our initial observation certainly holds many fascinating clues for our team and others around the world to explore,” says Light.

Meanwhile, the fat cells beneath our skin, according to the research team, could also be a kind of peripheral biological clock.

“It’s early days, but it’s not a giant leap to suppose that the light that regulates our circadian rhythm, received through our eyes, may also have the same impact through the fat cells near our skin,” says Light. “That’s why you are not supposed to look at digital devices before bed, because they emit the same blue light the sun does, which signals us to wake up.”

Interestingly, Light says the finding resulted from a bit of serendipity. The team was examining ways to use fat cells for insulin production through sunlight as a mean to aid diabetes patients.

“We noticed the reaction in human tissue cells in our negative control experiments, and since there was nothing in the literature, we knew it was important to investigate further,” he says.

Light and his team published the study in the journal Scientific Reports.

About Ben Renner

Writer, editor, curator, and social media manager based in Denver, Colorado. View my writing at

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