Staying Trim in the Winter

As summer ends and quickly gives way to winter, many of us start to notice our waistbands becoming a bit tighter—and it may not be from the long-legged underwear. The truth is, this extra padding has something to do with our eating habits. As the weather continues to get colder, we often find ourselves craving extra carbs. I often catch myself eating extra servings of potatoes and taking a piece of cake that is ‘just a little bigger’ than normal. I may even sneak a cookie or two if the situation permits.

The holidays may have something to do with this, but nature plays the prominent role. It turns out, that we simply tend to eat more in the fall and winter. A study conducted at the University of Georgia documented that subjects consumed about 200 more calories per day when the days started getting shorter in the fall. Also, in spite of their larger meals, they actually felt hungrier after eating[1].

What’s going on here?

In the animal kingdom, we see that many species gain weight in the fall to help them survive the winter. Although the extra fat does insulate them, there are also other factors at play. For instance, bears gain weight to sustain themselves for a long winter hibernation. Other animals, such as deer, may need to burn that fat for energy as the plants they eat die or are hidden by snowfall.

But is this really the case with humans? In our modern society, we don’t have to worry too much about food shortages in the winter. And while it gets cold outside, we can take shelter in our warm houses. Is there more going on here than meets the eye?

It may sound strange, but our eating habits during the winter are caused by a lack of sunlight—the same thing that causes winter! It’s a pretty fascinating and complex process:

Are you happy or a little SAD?

Sunlight is known to boost our levels of serotonin, a brain chemical often called the “happiness hormone” because it is known to improve mood[2]. In the winter, our serotonin levels tend to drop due to decreased sunlight exposure. In fact, there is actually a form of depression that is caused by lack of sunlight during the winter; it’s known as SAD (Seasonal Affective Disorder). Each year, it affects 25 million Americans (a majority of which are women). Some of its symptoms include: depression, napping, low self-esteem, irritability, and shyness[3].

This is how sunlight relates to your diet: Tryptophan, which is an amino acid and building block of serotonin, enters our brain through dietary sources. When tryptophan enters our brain, our brains use it to create serotonin[4]. Thus, in an attempt to combat SAD—or the simple moodiness that results from low serotonin levels—our bodies begin to crave sugary or starchy foods. When we eat these foods, tryptophan is released into our brains and we experience a temporary rise in serotonin levels[5].

Watch what you eat

As you may have guessed, this is not the ideal solution to the problem. The serotonin boost we get from starchy or sugary foods is short lived[6]. After we consume them, these foods quickly cause our blood sugar and insulin levels to spike. This causes us to crash into hypoglycemia (low blood sugar). When this happens, we start to feel shaky, nervous, lethargic and fatigued. Besides this, we quickly become hungry for more sugary and starchy foods[7]. As this cycle continues to repeat, we consume too much food and the pounds can begin to pile on.

Another thing to avoid is animal protein (meat and dairy). These foods actually cause the tryptophan levels in the brain to decrease. A study conducted on this issue showed that a breakfast high in animal protein—consisting of turkey, eggs, and cheese—caused a significant drop in brain tryptophan levels. However, those eating a breakfast consisting of waffles and orange juice saw their brain tryptophan levels rise[8].

Eat wisely

What we really need to do is eat wisely. We need to eat complex (unrefined) carbohydrates, such as whole grains. Besides containing the tryptophan we need to create serotonin, these foods will be much better for our bodies. The fiber they contain will keep us full and satisfy our food cravings. This means we won’t have to deal with those ugly blood sugar swings that keep us craving sugar every couple of hours.

Of course a balanced diet consisting of whole grains, fruits, vegetables, nuts, and legumes (lentils, beans, and peas) is ideal. A proper diet will improve your energy and keep you healthy as well. If you get cravings for something sweet, opt for a piece of fruit instead.

One thing you should consider adding to your diet is seeds, such as sesame, sunflower, and pumpkin seeds. Seeds contain a high tryptophan to total protein ratio[9]. Normally, tryptophan is found in smaller amounts and has to compete with other amino acids to reach your brain. However, since seeds contain high levels of tryptophan, the tryptophan will have an easier time making it to your brain[10]. Another great source of tryptophan is tofu. It’s also high in protein and has a good ratio of tryptophan to other amino acids.

See the light

Exposure to bright light is a good way to increase serotonin in your brain. In fact, the standard treatment for SAD is called phototherapy or light therapy. The idea is pretty simply, doctors expose people to very bright light at regular intervals. This can temporarily increase the tryptophan (and serotonin) levels in your brain. In one study, constant exposure to bright light was actually shown to block the mood-worsening effects of tryptophan depletion entirely[11].

This is good news for us! What it means is we simply need to spend some more time in the sun. It’s a natural way to boost serotonin and is a lot cheaper than phototherapy sessions. Think about it, only a few generations ago, most of the world population was involved in agriculture and spent most of their day outside. Even in the winter or on cloudy days, this would have provided people with enough of sun exposure to keep their serotonin levels high[12].

So lets remember to go outside and spend a little more time in the sun. Do some yard work, play a sport or even take a short walk outside when you have a break. If it’s just too cold for you, try to sit closer to the windows when the sun is coming in. Even a little more exposure to the sun will brighten your day and help alleviate cravings.


While you are spending time outdoors, why not exercise? Exercise has been clearly demonstrated to have both antidepressant and antianxiety effects[13]. There are several lines of research, suggesting that exercise increases brain serotonin function. Researchers believe this is due to an increase in tryptophan availability to the brain after exercise[14].

So make an effort to get some more exercise in the winter. Besides the boost in serotonin you experience, you’ll also be working off the extra calories you may have eaten! If you’re from a cold climate, participate in winter sports. I’m originally from Minnesota and when I was young, I actually enjoyed the outdoors more in the winter than in the summer!

If it gets too cold outside for you to jog or bike as normal, join a gym. That way you can use the treadmills, ellipticals and stationary bikes for a few months and move back outdoors when the weather clears up. Another idea to consider is pursuing different sports or activities during the winter than you did in the summer. Try basketball, racquetball, or maybe give weight lifting a try. This will give you some variety and may even work muscles you had been missing while doing your typical exercises.

Concluding thoughts

So there you have it, your recipe for staying fit in the winter: Eat a balanced diet full of fruits and vegetables and limit you intake of sweets and simple carbohydrates (white bread, rice, sugar, potatoes etc.). Also, stay away from soft drinks and fruit juices; these drinks contain a lot of empty calories from sugar. If you’re having trouble with food cravings, you can also try adding soup to your diet. People eating soup before a meal have been shown to eat fewer calories. Other than this, make sure to spend some time outside in the sun; and while you’re at it, get a little exercise. Simply going for a short walk in the sun and fresh air will do you a lot of good.

[1] De Castro, J M. “Seasonal Rhythms of Human Nutrient Intake and Meal Pattern.” Physiology & Behavior 50, no. 1 (July 1991): 243–248.

[2] “How To Boost Serotonin Naturally |” Accessed November 26, 2012.

[3] “Foods That Boost Serotonin and Help Fight Winter Depression.” Web MD.

[4] “Preventing Winter Weight Gain.” Psychology Today.

[5] Ibid

[6] Ibid

[7] Ibid

[8] Hudson, Craig, Susan Hudson, and Joan MacKenzie. “Protein-source Tryptophan as an Efficacious Treatment for Social Anxiety Disorder: a Pilot Study.” Canadian Journal of Physiology and Pharmacology 85, no. 9 (September 2007): 928–932. doi:10.1139/Y07-082.

[9] “How To Boost Serotonin Naturally |” Accessed November 26, 2012.

[10] Ibid

[11] Aan het Rot, Marije, Chawki Benkelfat, Diane B Boivin, and Simon N Young. “Bright Light Exposure During Acute Tryptophan Depletion Prevents a Lowering of Mood in Mildly Seasonal Women.” European Neuropsychopharmacology: The Journal of the European College of Neuropsychopharmacology 18, no. 1 (January 2008): 14–23. doi:10.1016/j.euroneuro.2007.05.003.

[12] Young, Simon N. “How to Increase Serotonin in the Human Brain Without Drugs.” Journal of Psychiatry & Neuroscience : JPN 32, no. 6 (November 2007): 394–399.

[13] Ibid

[14] Ibid

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Jon Ewald, MD

Jon Ewald grew up in Minnesota and has a love for the outdoors. He obtained his medical degree at Loma Linda University, graduating in 2020. He is currently completing his residency in Radiology at University of Pittsburgh.

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