Feel like you gained a few pounds this winter?

You're not alone and in turns out there's clear reasons why we tend to gain our weight during the winter months.

Cold weather and appetite effects can go hand-in-hand. Hibernating animals tend to store fat before winter by increasing enzymes that increase fat storage (lipoprotein lipase). In a study published in the Journal of Clinical Endocrinology and Metabolism, this was clearly shown to occur in humans as well. Humans increased fat storage enzymatic activity just like bears, for example.

Cortisol, a well know fat storing appetite increasing hormone, increases in winter and drops in summer. You can easily accumulate up to 10 pounds if cortisol levels increase by 30%.

SAD (seasonal affective disorder), a well known winter phenomena that affects many people, affects serotonin levels which control food intake. People who suffer from SAD have an almost compulsive attraction to carbohydrates. They are also often isolated at home eating more with less activity. When I worked in Canada some of my SAD patients would gain 30 pounds over the winter and only lose about 10 pounds over the summer. In 10 years, that is a 200 pound weight gain.

Leptin and Cold Weather

Leptin, a well known body weight regulator, has been clearly shown to drop when humans are exposed to cold. When leptin levels drop, your body thinks you are starving and you eat more. We've also seen that people who swim in cold water get much hungrier than people who swim in warmer waters.

In the European Journal of Clinical Nutrition, it shows that people gained about 1 to 2 pounds per winter and ate an additional 86 calories per day. This might not sound like much but in a 6 month winter, that’s over 15,000 calories or about 4.5 pounds. Over 10 years that adds up to 45 pounds.

Beside the holidays, which I call the danger zone between Halloween and New Year’s, there are many biological reasons that people gain weight. For now, we get to enjoy the warm weather that summer brings!