Winter Holiday Weight Gain and Related Biological Causes

There are changes in the chemistry of the brain during the fall and winter.

Posted Nov 24, 2016

Perhaps some of us have successfully lost weight over the past few months and are panicking over the potential weight gain associated with the holiday season.

I know you are shaking your head: “Not me, not this year.”

Here is why I am shaking my head up and down instead of right to left: Research has consistently shown that on average, most Americans gain weight over the holiday season. But why?

1) Holidays are in the Fall/Winter

Studies have shown that on average, Americans consume more calories in these seasons. Dr. Ma, at the University of Massachusetts, has shown that daily caloric intake was higher by 86 kcal per day starting in the fall, and that the increase in calories came mainly from total and saturated-fat intake1. According to Dr. de Catro, we eat more starting in the Fall and desire larger meals to be satisfied2.

But why do we eat more in the winter?

There are seasonal biological changes that facilitate this increase in caloric intake. For example, some of the feel-good brain chemicals decrease in the winter; the one most talked about is serotonin because it’s implicated in food consumption patterns, mood, and other important social behaviors.

In one study, researchers found that post-mortem brain specimens contained less serotonin metabolites in the winter3. When serotonin is depleted, we crave carbohydrates, and we feel down. This is an important feedback mechanism, because carbohydrate consumption increases serotonin release. If you are a female, you might have experienced an increase in carbohydrate cravings and sadness during PMS, when serotonin levels are low. So, during the winter, we increase food intake to make ourselves feel better, compensating for the decrements in the feel good brain chemicals.

Second, the day gets shorter and colder in fall and winter, which promotes a more sedentary life-style.

The problem is exacerbated when we are also surrounded with scrumptious leftovers from all the holiday parties. All of a sudden, we find ourselves dipping the deformed apple pie slices directly into a pint of ice cream.

Also, as the day gets shorter and our exposure to daylight is decreased, brain chemicals such as serotonin decrease with it. This explains why many people experience winter blues. Being stranded at home because of the darkness, cold, and depressed mood, all while being surrounded by plenty of mood-enhancing foods, is a recipe proven to cause weight gain.

2) We have strong associations between holidays and specific foods.

These are well-learned, strong links ingrained in our memory and comfortably residing in our unconscious. We have many well-established food associations; for example between birthdays and birthday cakes. Along the same vein, there are certainly holiday foods—decorative cookies, pies, and other high-sugar and high-fat foods.

Also, we get invited to multiple holiday parties, work parties (of course we have to go with our partners, and they have to reciprocate), family dinners, and New Year’s Eve—with plenty of appetizers and junk at all-night-long gatherings, not to mention the festive, calorie-saturated drinks.

3) This is an economically stressful time.

This is the shopping season, whether we're buying presents for others or taking advantage of the sales for ourselves. This might add additional financial and social stress, and stress makes some of us eat junk.

Unfortunately, stress selectively packs the weight gain in the middle, extending our waistlines.

Is there anything else gained—other than weight?

Yes, yes, and yes!

The holidays make us happy overall. There is another brain chemical that is also affected by the onset of the holidays—a socially induced one.

We certainly become more social around the holidays. For many of us, the only time we see our families is over the holidays. We are all born with the intrinsic need to affiliate and crave social interactions. These interactions are promoted and rewarded by oxytocin, a brain chemical responsible for the desire to meet a good friend for coffee to talk about nothing important.

Let’s all keep it real this holiday and respect our biological and social natures. Let’s give ourselves permission to increase food intake and not feel guilty about it.

However, let’s also have some general guidelines to make the best out of this:

1. When given a choice between high-fat and high-calorie desserts, go for the high-fat one.

2. Always have a big to-go cup (preferably not disposable) filled with your favorite herbal, non-caffeinated drink.

Mint, raspberry, ginger, lemon, anise, cinnamon, or a mixture of teas are some suggestions—I love pomegranate, hibiscus and raspberry. If you like them sweetened, sweeten with natural honey and not processed white sugar. Invest in a personalized non-disposable cup with a very safe lid, and take it everywhere. This habit leaves your stomach always partially full.

3. If you have the choice between cake and ice cream, go for natural ice cream.

Ice cream has a high percentage of calcium, whereas many cakes have no nutritional value.

4. Share your favorite desserts.

Making others fat makes you look skinny. Okay, just kidding: Sharing gets your oxytocin high, makes you happier and decreases the amount of calories and fat consumed, but still satisfies your nagging cravings.

5. Avoid commercials displaying mouth-watering foods.

Make your phone calls, offer to make tea, go to the bathroom, whatever you can do to avoid watching these commercials.

6. Don’t start a strict diet during the holidays.

Many diets end up depleting the brain of amino acids required to make serotonin, which causes depressed mood and irritability. Don’t make it hard on yourself during a time when your biology is already making you vulnerable. Don’t miss out on good memories because you have to decline some holiday invitations or ruin others’ spirits because your diet is making you irritable and difficult to accommodate.

Happy holidays!


1. Ma, Y., Olendzki, B., Li, W., Hafner, A., Chiriboga, D., Hebert, J., … Ockene, I. (2006). Seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population. European Journal of Clinical Nutrition, 60(4), 519–528.

2. de Castro, J.M. (1991). Seasonal rhythms of human nutrient intake and meal pattern. Physiology of Behavior, 50 (1): 243-248.

3. Gupta, A. Sharma, P. K., Garg, V. K., et al. (2013). Role of serotonin in seasonal affective disorder. European Review for Medical and Pharmacological Sciences. 2013 Jan;17(1):49-55.