So what's up with winter weight gain? From a naturopathic standpoint, it becomes important to evaluate all of the possible contributing factors. Firstly, because it's cold, our bodies crave heavier foods, more carbohydrates and denser meals. These types of meals are generally higher in calories. Surprisingly, these cravings usually start in the brain: serotonin naturally decreases in the fall and winter months due to a decrease in sunlight exposure. This can contribute to the onset of SAD (seasonal effective disorder), an increase in blood pressure, an increase in pain sensitivity and sleep disturbance. Carbohydrates, because of their effect on insulin release, can contribute to the increase in serotonin production, increasing circulating serotonin levels resulting in mitigation of the above side effects of low serotonin. However, excess carbohydrates can also contribute to the unfortunate side effect of a few winter pounds!
A second and very important factor to the December "Butterball" transformation that happens to a few of us in the winter is the association between light and thyroid function. Although, after 4 weeks of light therapy test subjects did not show changes in typical blood measures for thyroid function (thyroid function panel), tests did show a decrease in circulating reverse T3 levels. What one may extrapolate from this result is that people that exposed are to less light have a higher amount of reverse (or unactive) thyroid hormone. When these subjects are exposed to light again, their bodies have an increased amount of active thyroid hormone which results in an increase metabolic function (less weight gain and more energy)!