Winter weight gain explained by lack of sunlight, suggests study

Olivia Petter

There’s just something about winter.

Whether it’s the endless string of cosy nights in or the myriad of sumptuous puds and pies on offer in the supermarkets, this time of year seems to be synonymous with indulgence.

But is there more to winter weight gain than the art of letting oneself go at Christmas and beyond?

According to new research, the real reason why our clothes feel particularly snug these days extends beyond the bounds of sheer gluttony - it could actually be down to not having enough sun exposure.

Scientists at the University of Alberta found the fat cells that sit beneath the skin can actually shrink when exposed to blue light emitted by the sun.

"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," explained Peter Light, lead author of the Scientific Reports (by Nature) study.

This breakthrough finding led Light and his team to believe that the opposite could be true when exposure to sunlight was limited i.e. during the shorter days that occur in winter.

He noted that this effect would be particularly prevalent for those living in a northern climate.

"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," the pharmacology professor added.

However, he went on to warn that his findings should not be conflated as advocation of exposure to sunlight for weight loss.

He explained that further research would be necessary in order to fully determine how much light exposure is required to activate fat cell shrinkage.

Light added that his findings were “serendipitous” and that his team had set out to investigate how light could help him to bioengineer fat cells to produce insulin in order to support Type 1 diabetes patients.

"It's early days,” he said, “but it's not a giant leap to suppose that the light that regulates our circadian rhythm (also known as our sleep/wake cycle), received through our eyes, may also have the same impact through the fat cells near our skin."