A new study suggests that our exposure to sunshine (or lack of it) can promote or reduce the amount of fat in our bodies.
Researchers from the University of Alberta's Diabetes Institute found that blue light from the sun causes the fat cells that lie just beneath our skin to store less fat than usual.
Essentially this means that when our bodies are exposed to plenty of sunshine they may burn fat, whereas when we don't get enough, our bodies begin to promote fat storage, possibly contributing to weight gain over the long winter periods. So says Peter Light, senior author of the study.
However, he cautions that these are only initial observations and that staying out in the sunshine for extended periods is not a recommended or proven way to lose weight.
"For example, we don't yet know the intensity and duration of light necessary for this pathway to be activated," he said.
Despite this, the findings could one day lead to treatments for obesity and diseases such as diabetes.
"Maybe this mechanism contributes to setting the number of fat cells we produce in childhood—thought to stay with us into adulthood," he speculated.
The findings suggest that the fat cells in our skin may, in some way, be linked to our biological clock or circadian rhythms.
"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," he said.
The exposure to sunlight that dictates our sleep-wake patterns may also affect how we burn fat, depending on the season. This may may have an evolutionary basis, according to Hand. "You gain weight in the winter and then burn it off in the summer."