Scientists uncover surprising cause of winter weight gain

It’s typical to gain a few extra pounds over the winter, right?

You may eat more over the holidays. Plus, you probably don’t get outdoors as much to walk, exercise, or do yard work.

But there’s another important factor at work that impedes your ability to keep the pounds off during the winter…

Lack of sunlight.

Between October and April, the sun simply isn’t high enough in the sky in most parts of the country to activate vitamin D production in the skin. And older people — especially older women — may gain weight if they have low vitamin D levels.

In fact, in a 2012 study published in The Journal of Women’s Health, researchers followed more than 4,600 women aged 65 and older for five years.

Those with insufficient levels of vitamin D in their blood gained about two pounds more than those who had adequate levels of the vitamin during a five-year study.

That amount of weight gain may seem small, but it’s important to note the women with insufficient levels of vitamin D also weighed more when the study began than women with normal vitamin D levels. So, I suspect the low vitamin D-weight gain link goes back years in these women.

In the new 2017 study, published in Scientific Reports, Canadian researchers found that fat cells beneath our skin actually shrink when exposed to the sun’s blue light wavelengths (the light visible to the human eye).

The study’s aptly named lead researcher — Peter Light — says when these wavelengths penetrate our skin and reach the fat cells just beneath it, lipid (fat) droplets reduce in size and are released out of the cells. In short, our cells literally shrink and excrete fat when exposed to natural sunlight.

Of course, vitamin D does a lot more than just help you stave off winter weight gain.

As I recently reported in my Insiders’ Cures newsletter, the spike in “winter” heart attacks doesn’t actually stem from shoveling snow or the cold temperature — that’s a common misconception. Instead, research links it to lack of vitamin D, which the heart critically needs. (You can read all about that research in the January 2018 issue of my newsletter. If you’re not yet a newsletter subscriber, now’s the perfect time to get started.)

And just yesterday I told you how this essential nutrient can actually repair cardiovascular damage that’s already been done to the heart. In other words, it can help your heart heal itself.

Furthermore, I haven’t even touched on the many other critical roles vitamin D plays in the body ¾ from immune system support to disease prevention to mood stabilization.

So  as the light stays low and the weather remains chilly, it’s more important than ever to supplement daily with 10,000 IU of vitamin D. (And remember, that dose may sound high, but that’s not the case when it comes to international units (IU).)

You can now find vitamin D in handy liquid form with the powerful marine carotenoid astaxanthin. So, rather than taking more pills, you can simply add it to a healthy beverage of your choice. (You can find more information about these ingredients via

In addition, be sure you know your blood levels. Ask your doctor at your annual check-up to test your vitamin D levels with a 25(OH)D test. Ideally, you want your levels to be between 50 nmol/L and 75 nmol/L.

Lastly, when the weather finally starts to break this spring, make sure you get outside for some healthy sun exposure every day. You may find that those extra, cold-weather pounds will quickly melt away, along with the ice and snow.



Associations Between 25-Hydroxyvitamin D and Weight Gain in Elderly Women Journal of Women’s Health. October 2012, 21(10): 1066-1073.

“Subcutaneous white adipocytes express a light sensitive signaling pathway mediated via a melanopsin/TRPC channel axis,” Scientific Reports 2017; 7: 16332