We’ve all been through the cold, dark days of winter and noticed that we've started to fatten up a bit. Most of us attribute that winter weight gain to the frequent holiday feasts—or the bitter cold that keeps a lot of people bundled up indoors, perched squarely in front of the TV.
But winter weight gain might have another culprit: lack of sun.
That's because the sun's blue light can shrink fat cells near the skin's surface, according to a new study from Canada's University of Alberta.
"When the sun's blue light wavelengths—the light we can see with our eye—penetrate our skin and reach the fat cells just beneath, lipid droplets reduce in size and are released out of the cell. In other words, our cells don't store as much fat," said study senior author Peter Light, Ph.D., a professor of pharmacology and the director of UAlberta's Alberta Diabetes Institute. "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 contribute to the typical weight gain some of us have over winter."
We imagine lots of Canadians—and plenty of other people in cold climates—can relate.
Researchers stumbled upon the revelation when they were trying to help patients with Type-1 diabetes by creating fat cells that could be coaxed into making insulin when exposed to light. They discovered that regular fat cells respond to light using the same "molecular trail" activated when blue light hits our eyes; that chemical trigger helps regulate our circadian rhythms and the sleep/wake cycle. The researchers speculate that the process in fat cells may be related to evolution and surviving colder climates since in humans the fat is spread fairly evenly underneath the skin, distinct from most mammals.
If you've noticed a little bit of winter weight creeping around your waistline, try this heart-racing workout to warm up when it's freezing outside.