6 Surprising Reasons You Gain Weight in the Winter


6 Surprising Reasons You Gain Weight in the Winter to Know

Winter is not the time to let your guard down, at least with regards to your waistline. The chilly weather brings with it the risk of unwanted weight gain. In fact, the average person gains about 3 pounds during the long, cold months of winter. It’s one thing if you take those extra pounds off when spring arrives but that doesn’t always happen. An extra 3 pounds yearly adds up! Of course, weight gain in the winter varies and some people make it through the holidays and the dark days of January and February without gaining a pound. Let’s look at why weight gain in the winter is common and what you can do to prevent it.

Gain Weight In The Winter: Your Biological Clock is Off Kilter

All the functions in your body, including the activities of hormones, brain chemicals, and even your body temperature is regulated by your master biological clock. This clock is built around a 24-hour cycle and is sensitive to night and day as well as environmental temperature. This master clock is made up of clusters of nerve cells collectively called the suprachiasmatic nucleus, or SCN, located near the hypothalamus in the brain. It’s this clock that sets your circadian rhythms, the natural ebb, and flow of hormones and other bodily processes. Even your cells dance to the beat of your biological clock and circadian rhythms.

Unfortunately, this master clock is easily disrupted. What happens in the autumn when you “fall back” and set your clocks back an hour? The time change disrupts your master, internal clock and, in turn, circadian rhythms. Yes, even an hour adjustment in the time can change your body’s natural rhythms. In fact, studies have linked setting the clock forward and backward twice a year with an increased risk of heart attacks and traffic accidents. Disruption in circadian rhythms is also linked to a higher risk of depression, type 2 diabetes, and obesity. When your internal bodily processes are disrupted, along with hormones and brain chemicals, it can change appetite hormones and brain chemicals that regulate your appetite. These disruptions can also interfere with sleep. As you know, lack of sleep is linked with weight gain as well.

How to Prevent It:

Expose your eyes to light as much as you can during the day and sleep in a completely dark room at night. This helps maximize the production of melatonin, a hormone involved in the sleep-wake cycle and circadian rhythms.

Gain Weight In The Winter: You Don’t Get Enough Vitamin D

Unless you take a vitamin D supplement, you get most of your vitamin D from exposing your skin to the sun. Unfortunately, you get fewer opportunities to do that in the winter. Although you can store vitamin D, most people are marginally low and winter makes the problem worse. Why is this important? Studies link low levels of vitamin D to weight gain and obesity.

How to Prevent It:

Ask your doctor to check your vitamin D level via a blood test. If it’s low, you may need a vitamin D supplement. Otherwise, get outdoors as much as you can in the winter or head south for a vacation mid-winter.

Gain Weight In The Winter: You’re Spending More Time Indoors

Even if you do a regular workout at home, you spend less time out and about doing unstructured exercise when the temperature drops. It’s harder to visit the mall, take a leisurely walk, or do outdoor activities like gardening and hiking that burn calories. What you do when you aren’t doing a structured workout matters. You can burn a significant number of calories just staying more active during the day. Winter puts a damper on that.

How to Prevent It:

Keep working out but also be aware of how much you’re moving throughout the day. A fitness tracker is useful during the winter months for monitoring your activity level. Look for opportunities to move more.

Gain Weight In The Winter: Holiday Nibbles

Even if you commit to not overeating during the holidays, those “little bites” of cookies you’re baking for a party or samples of Aunt Mary’s holiday brownies add up. The holidays are very food and calorie focused.

How to Prevent It:

Winter is a good time to keep a food journal, so you’re aware of how much you’re eating and drinking. When you nibble a little here and a little there, it doesn’t seem like much while you’re doing it but when you tally it up over the course of a day, it’s significant. Indulge a little around the holiday but keep tabs on how often you’re doing it. On those days when you indulge, increase your activity level.

Gain Weight In The Winter: Your Body is Primed to Gain Weight

One theory as to why we gain weight has to do with our ancestors. In earlier times, carrying more body fat during the winter was an asset. During the winter, at least in primitive times, finding food was harder and you needed energy reserves to survive the harsh temperatures and lack of food. Our bodies might be “primed” to store fat when the temperatures drop and let up a bit on fat storage in the spring and summer. When winter arrives, your appetite hormones increase your appetite and you unconsciously move less, all in the name of survival. Fortunately, famine isn’t an issue for most people in Western countries. We have the opposite problem these days – an abundance of food and too much of the wrong kind.

How to Prevent It:

You can’t reprogram your genes or how your body responds based on its evolutionary history but you can be more aware of your daily habits. That’s where keeping a food journal comes in. Of course, you don’t want to neglect the other part of the equation – exercise. The take-home message is awareness and mindfulness. That’s important at all times of the year, but particularly in the winter.

Gain Weight In The Winter: You’re Feeling a Bit Down

As mentioned, less sunlight in the winter can disrupt your biological clock. For some people, lack of sunlight leads to the “winter blues,” feelings of being down and less motivated to do things. A more severe form of the blues is called seasonal affective disorder, a condition that up to 20% of the population suffers from on a seasonal basis. One way that people with seasonal affective disorder “self-medicate” is by eating carby foods. In fact, 75% of men and women who suffer from this seasonal form of depression gain weight. Not surprising since you’re eating more and probably feel less like exercising.

How to Prevent It:

If you’re only experiencing a mild case of the blues and loss of energy and motivation, it may be enough to expose your eyes to daylight more. However, if you have severe symptoms, talk to your doctor. One safe and effective therapy is to invest in a special light box that exposes you to wavelengths of light similar to what you soak up outdoors.  Exposing your eyes to a light box helps normalize brain chemicals that may have gone awry with the advent of cooler weather and less exposure to light.

The Bottom Line

Now you know why it’s easy to gain weight in the winter – but being aware is part of the battle. Keep tabs on what you’re eating and how much you’re moving, even if you have to invest in a fitness tracker to give you feedback. Don’t let your body go into hibernation this winter.



National Institute of General Medical Sciences. “Circadian Rhythms Fact Sheet”

Health. “7 Signs of Seasonal Affective Disorder”

Circ Res. 2010 Feb 19; 106(3): 447–462.doi:  10.1161/CIRCRESAHA.109.208355.

J Neuroendocrinol. 2003 Apr;15(4):432-7.

J Womens Health (Larchmt). 2012 Oct; 21(10): 1066–1073.


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