The Surprising Reason People Gain Weight in Winter Months
"We found that if you expose fat cells to two to four hours of blue light daily for two weeks, they contain significantly less fat within them," says study co-author Peter Light, PhD., professor at the University of Alberta. (Blue light comes most intensely from the sun.)
Researchers have two theories as to what's going on: Blue light either stimulates fat cells to release fat or prevents them from storing fat as easily. And because the study showed that fat cells exposed to light released more glycerol (a component of fat when it's been broken down) and reduced the size of fat droplets, it's more likely they're releasing fat, says Light.
So why are your fat cells light-sensitive? "The same mechanism found in your eye that responds to daylight and nighttime is actually found in your fat cells," Light says. The only difference is that your eye is transparent, so you don't need a lot of blue light to wake you up (one reason why experts say not to look at electronic devices before bed). However, your skin is more impermeable. "Only about 1 to 5 percent of blue light actually penetrates the skin," says Light, "and the level of intensity needed is found only in the sun."
The research is still in its early days, so it's too soon to be able to tell you exactly how much time you need outside to reap this benefit. But given that regular sun exposure may prompt your body to store less fat—and the flipside being that insufficient sun may prompt your body to store fat and lead to weight gain—it's all the more reason to get outside and enjoy the fresh air today...or once spring returns.