What happens to metabolism during winter? The surprising science of cold adaptation

November 17, 2025 •

4 min read

According to a study published in the journal Physiology & Behavior, the metabolic rate can increase by as much as 11.5% in winter compared to summer, even under mild cold exposure. This surprising fact challenges the common misconception that our metabolism slows down during colder months, explaining what happens to metabolism during winter as a complex process of adaptive thermogenesis.

Quick Summary

The body increases its metabolic rate during winter through shivering and non-shivering thermogenesis to maintain core temperature. Hormonal shifts and lifestyle changes often drive increased appetite and sedentary behavior, which can lead to weight gain. Understanding these mechanisms helps manage health in cold weather.

Key Points

Metabolism Increases: Your metabolic rate does not slow down in winter; it increases to produce more heat and maintain core body temperature.
Brown Fat is a Key Player: A specialized type of fat, known as brown adipose tissue (BAT), is activated by cold to burn calories and generate heat without shivering.
Behavioral Changes Drive Weight Gain: Increased appetite, cravings for high-calorie foods, and reduced physical activity typically overpower the minor metabolic boost from cold exposure, leading to winter weight gain.
Hormones are a Factor: Longer nights and less sun exposure lead to higher melatonin and lower serotonin, which can increase cravings for carbohydrates and contribute to seasonal mood changes.
Actionable Lifestyle Strategies: You can optimize your winter metabolism by prioritizing indoor exercise, managing diet and cravings, staying hydrated, and ensuring adequate Vitamin D and sleep.

The Science of Cold Adaptation

When temperatures drop, the human body is equipped with sophisticated physiological mechanisms to maintain a stable internal core temperature, a state known as homeostasis. This process, called thermoregulation, relies on increasing the body's metabolic rate, or thermogenesis, to generate the necessary heat. Contrary to the old belief that metabolism simply becomes sluggish in winter, the reality is a nuanced and proactive metabolic response designed for survival.

Shivering and Non-Shivering Thermogenesis

To combat cold, the body primarily employs two methods of thermogenesis:

Shivering Thermogenesis (ST): This is the more familiar response, involving rapid, involuntary muscle contractions that generate heat as a byproduct of movement. Shivering can increase your body's heat production significantly, burning a considerable number of calories in the process. However, it is an energetically expensive and short-term solution, as muscle fatigue limits its sustainability.
Non-Shivering Thermogenesis (NST): This process generates heat without muscle contraction and is driven by the activation of brown adipose tissue (BAT), or brown fat. Unlike white fat, which stores energy, brown fat is specialized to burn calories to produce heat. Cold exposure activates BAT, prompting it to metabolize blood sugar (glucose) and fat molecules, efficiently turning them into heat. The more active your brown fat is, the more calories you burn for thermogenesis.

The Role of Brown Fat in Winter Metabolism

Brown fat was once thought to exist only in babies, but recent research has confirmed its presence and metabolic activity in adults, especially those with healthier metabolisms. Cold stimulation is a potent activator of brown fat, leading to increased thermogenesis. Studies have shown that even mild cold exposure can stimulate BAT, contributing to higher resting metabolic rates. This activation can be triggered by simply lowering the thermostat or taking cold showers.

The Behavioral Paradox of Winter Weight Gain

Despite the body's biological impulse to increase metabolism in winter, many people experience weight gain. This is largely due to behavioral and hormonal factors that counteract the minor metabolic boost from thermogenesis.

Appetite and Cravings

Evolutionary instincts play a role in driving us toward high-calorie, nutrient-dense foods in preparation for a potentially scarce winter. Additionally, hormonal changes influence appetite. Melatonin levels, which regulate our sleep-wake cycle, are higher in winter due to less daylight, which can also affect appetite and lead to cravings for carbohydrates. Lower serotonin levels, sometimes associated with Seasonal Affective Disorder (SAD), can also increase the desire for mood-boosting carbs.

Sedentary Lifestyles

Shorter days and colder weather naturally lead to reduced physical activity. We are more likely to spend time indoors, engaging in sedentary activities, which dramatically reduces overall calorie expenditure. This decrease in exercise often outweighs the relatively small increase in thermogenesis, leading to a caloric surplus and subsequent weight gain.

Comparing Metabolic Effects: Winter vs. Summer


Feature	Winter Metabolism	Summer Metabolism
Energy Expenditure	Slightly increased due to thermogenesis (shivering and BAT activation).	Normal resting metabolic rate, with some increase from activity and heat regulation (sweating).
Hormonal Profile	Higher melatonin, potentially lower serotonin, and fluctuating leptin, which can stimulate appetite.	Appetite may be suppressed by heat; balanced hormonal signaling.
Appetite & Cravings	Increased desire for calorie-dense "comfort foods" and carbohydrates.	Craving for lighter, water-rich foods like salads and fruits.
Physical Activity	Often reduced due to cold weather, leading to a more sedentary lifestyle.	Typically higher, with more outdoor activities and longer daylight hours.
Vitamin D	Lower levels due to less sunlight, which can impact metabolic function.	Higher levels due to increased sun exposure.

Optimizing Your Winter Metabolism

While seasonal factors can work against your health goals, you can proactively manage your metabolism with strategic lifestyle choices. The key is to leverage your body's natural thermogenic response while mitigating the behavioral changes that lead to weight gain.

Here are some practical tips for a healthier winter:

Prioritize Regular Exercise: Counter reduced outdoor activity with consistent indoor workouts. Strength training builds muscle, which burns more calories at rest, and high-intensity interval training (HIIT) is efficient for calorie burning.
Embrace Mindful Eating: Be aware of increased cravings for comfort foods. Focus on nutrient-dense options like soups, stews, lean proteins, and fiber-rich root vegetables. Pay attention to portion sizes to avoid a calorie surplus.
Stay Hydrated: Dehydration can slow metabolism and is often mistaken for hunger. Drink plenty of water throughout the day, and consider warm herbal teas as a comforting, low-calorie alternative to sugary beverages.
Leverage Cold Exposure: Controlled, mild cold exposure, such as lowering the thermostat or finishing a shower with a short blast of cool water, can help activate brown fat and increase thermogenesis.
Boost Vitamin D: With less sunlight, it's crucial to ensure adequate Vitamin D intake, as deficiency can disrupt metabolism. Talk to a healthcare provider about safe supplementation.
Manage Stress and Sleep: High stress and sleep deprivation disrupt hormone balance, increasing cravings and fat storage. Prioritize quality sleep and stress-reduction techniques like meditation to support metabolic health.

Conclusion

What happens to metabolism during winter is a dynamic process of adaptation. The body instinctively boosts its metabolic rate through thermogenesis to fight the cold, activating calorie-burning brown fat and, if necessary, shivering. However, this biological increase is often overshadowed by lifestyle changes—reduced physical activity, increased comfort food intake, and hormonal shifts—that drive winter weight gain. By understanding this complex interplay between biology and behavior, you can make informed choices to support your metabolism and maintain a healthy lifestyle throughout the colder months. Rather than a time of unavoidable metabolic decline, winter can be an opportunity to optimize your body's natural calorie-burning abilities. NCBI, Physiology of Cold Exposure

Frequently Asked Questions

No, this is a common myth. In fact, your body's metabolism actually increases slightly in cold weather to generate more heat and maintain a stable core temperature, a process called thermogenesis.

Winter weight gain is usually due to behavioral changes rather than a slower metabolism. Reduced physical activity, increased appetite for high-calorie comfort foods, and hormonal changes often outweigh the small increase in calorie burn from thermogenesis.

Non-shivering thermogenesis is the body's process of generating heat without muscle contraction. It is primarily driven by brown adipose tissue (BAT), or brown fat, which burns calories to create warmth when exposed to cold temperatures.

Brown fat can be activated by exposure to mild cold temperatures, such as lowering the thermostat in your home, taking a cool shower, or spending short periods outdoors in cold weather.

While your body does burn some extra calories to stay warm, the overall increase is not significant unless you are performing very strenuous exercise in extreme cold. The benefits of exercising in cold weather are more related to the physical activity itself.

Less sunlight exposure in winter can lead to lower Vitamin D levels, which have been linked to metabolic disruptions. Reduced light can also impact circadian rhythms and hormones like serotonin, influencing mood and appetite.

Focus on consistent indoor exercise like strength training or HIIT, practice mindful eating to control portion sizes and cravings for comfort foods, stay well-hydrated, and ensure you get adequate sleep to regulate metabolic hormones.