Do you burn extra calories when cold? The science of thermogenesis

December 4, 2025 •

4 min read

Studies have definitively shown that human beings burn more calories in the cold, a natural physiological response to maintain core body temperature. This process, known as thermogenesis, is the body's way of generating heat and involves a significant increase in energy expenditure. It's a survival mechanism that leverages different types of fat and muscle activity to prevent the core body temperature from dropping too low.

Quick Summary

The body burns extra calories in cold temperatures through thermogenesis, activating brown fat and triggering shivering. The effect is modest for casual exposure but is a genuine metabolic response that can be safely leveraged.

Key Points

Thermogenesis Explained: Your body increases its energy expenditure, or metabolic rate, to generate heat when exposed to cold, a process known as thermogenesis.
Two Ways to Burn: Heat is generated through both involuntary muscle contractions (shivering) and the metabolic activity of brown adipose tissue (non-shivering thermogenesis).
Brown Fat is Key: Unlike white fat which stores energy, brown fat burns calories (fat and glucose) to produce heat and is activated by cold temperatures.
Effect is Modest, Not Massive: While the calorie burn is real, it's not a shortcut to significant weight loss. Studies show a modest increase in daily calorie expenditure for casual cold exposure.
Consistency Over Intensity: Regular, safe exposure to cooler temperatures—such as a cool room or cold showers—is more beneficial for enhancing brown fat activity than occasional, extreme bouts of cold.
Combine for Best Results: Cold exposure works best as a supplement to, not a replacement for, a healthy diet and regular exercise. Outdoor exercise is especially effective.
Safety First: High-intensity cold therapy like ice baths carries risks such as hypothermia and is not suitable for everyone, especially those with certain heart conditions.

The Science of Cold-Induced Thermogenesis

When your body is exposed to cooler temperatures, it must expend additional energy to maintain its core temperature at a stable 98.6°F (37°C). This biological phenomenon is called thermogenesis. The body relies on two primary mechanisms to generate this heat and, in the process, burn extra calories: shivering and non-shivering thermogenesis. While the effect might not be as dramatic as some myths suggest, the physiological response is undeniable and scientifically proven.

Shivering vs. Non-Shivering Thermogenesis

Shivering thermogenesis is the body's more immediate and noticeable reaction to cold. This involves the involuntary and rhythmic contraction of skeletal muscles, which produces heat as a byproduct of the energy used during muscle activity. According to some studies, intense shivering can burn a significant number of calories, with some estimates placing it at 100 to 400 calories per hour. However, this is a short-term, unsustainable response that quickly diminishes once you warm up or start moving.

Non-shivering thermogenesis, on the other hand, is a more efficient and sustained method of heat production that relies on a specialized type of fat known as brown adipose tissue (BAT), or brown fat. Unlike white fat, which stores energy, brown fat is metabolically active and burns calories to produce heat. This process can be activated even in mild cold conditions, without the need for shivering.

The Role of Brown Fat in Calorie Burning

For many years, scientists believed brown fat was only significant in infants, who use it to keep warm, but recent discoveries have confirmed its presence and activity in adults. Brown fat is found in small amounts around the neck, shoulders, and spine and is a potent calorie-burning tool. When activated by cold, it burns fat and glucose to generate heat. Studies show that people with more active brown fat tend to have lower body mass indexes (BMI) and better metabolic health.

Regular, mild cold exposure, such as taking a cold shower or keeping your home slightly cooler, can increase both the activity and volume of brown fat over time. This process is sometimes referred to as the "browning" of white fat, where some white fat cells take on the calorie-burning properties of brown fat.

How to Leverage Cold for a Modest Metabolic Boost

While cold exposure is not a magic bullet for weight loss, it can be a useful tool when combined with a balanced diet and regular exercise. Here are some simple, safe methods to incorporate cold-induced thermogenesis into your routine:

Cold Showers: End your normal shower with 30 seconds to a few minutes of cold water. Gradually increase the duration as you adapt.
Cooler Room Temperatures: Lower your thermostat a few degrees in the winter. This can provide mild, consistent cold exposure throughout the day.
Outdoor Exercise: Combining physical activity with cold weather is highly effective. Outdoor activities like brisk walking, cycling, or running in winter can amplify the calorie-burning effect, as your body works harder to stay warm.
Stay Appropriately Dressed: Resist the urge to overdress. Allowing your body to feel slightly cool forces it to activate its thermogenic processes, but be mindful not to let yourself get uncomfortably or dangerously cold.

The Modest Impact on Calorie Expenditure

While the concept is powerful, the real-world calorie-burning effect is often modest for most people. Studies involving participants spending full days in cooler, but not freezing, temperatures (around 60°F or 19°C) have shown an increase in daily energy expenditure of roughly 80 to 200 calories. For a short cold shower, the effect is even smaller, estimated at 50-100 additional calories per session depending on various factors. This is not a substitute for a calorie-controlled diet and regular exercise, but rather a complementary strategy.

Comparison of Fat Types and Function


Feature	White Adipose Tissue (White Fat)	Brown Adipose Tissue (Brown Fat)	Beige/Brite Fat
Primary Function	Energy storage	Thermogenesis (heat production)	Can perform thermogenesis
Appearance	Pale or yellowish	Brownish color due to mitochondria	Similar to brown fat when activated
Mitochondria	Few	High concentration	High concentration when activated
Location	Subcutaneous areas (belly, hips) and visceral	Neck, shoulders, spine, kidneys	Develops within white fat depots
Calorie Burn	Stores calories for future use	Actively burns calories to generate heat	Burns calories like brown fat
Activation	Not metabolically active for heat	Activated by cold exposure	Activated by cold and exercise

Potential Downsides and Safety Precautions

It is crucial to approach cold exposure safely. Extreme cold water immersion or prolonged exposure without proper protection carries serious risks, including frostbite and hypothermia. For weight loss, some studies have shown that cold exposure, particularly cold plunges, can increase appetite, potentially leading to increased calorie intake that negates the calories burned. Individuals with heart conditions or other chronic medical problems should consult a healthcare provider before attempting any form of cold therapy. Furthermore, the amount of additional calories burned varies significantly from person to person, depending on factors like body composition, genetics, and age.

Conclusion

Yes, you do burn extra calories when cold, thanks to the body’s natural thermogenic processes. This calorie expenditure is primarily driven by shivering and, more sustainably, by the activation of brown fat. While cold exposure can provide a modest boost to your metabolism, it is not a standalone solution for significant weight loss. It should be viewed as one component of a holistic approach to health that includes a balanced diet and consistent exercise. For those interested, safe and gradual integration of mild cold exposure can be a supplementary tool for enhancing metabolic health. For more detailed research on thermogenesis, you can explore academic sources such as this review on human physiological responses to cold exposure found on ScienceDirect.

Disclaimer: Always consult with a healthcare professional before making significant changes to your health regimen, especially concerning therapies involving cold exposure, as individual responses and risks can vary.

Frequently Asked Questions

The amount varies greatly depending on the temperature, duration, and individual factors like body composition and genetics. Studies suggest a modest increase in daily energy expenditure, potentially ranging from 80 to 200 calories for sustained exposure to cool temperatures.

No. White fat primarily serves to store excess energy, while brown fat is a specialized, metabolically active tissue that burns calories to generate heat. Brown fat gets its color from a high concentration of iron-rich mitochondria.

Cold showers can provide a modest metabolic boost by activating brown fat. However, they are not a powerful tool for weight loss on their own and should be combined with a healthy diet and regular exercise for meaningful results.

Shivering thermogenesis uses involuntary muscle contractions to produce heat, which is a rapid, short-term response to intense cold. Non-shivering thermogenesis is a more sustained, long-term process that relies on brown fat burning calories to generate heat without muscle movement.

Extreme or prolonged cold exposure can be dangerous, with risks including hypothermia and frostbite. Additionally, some research suggests it may increase appetite, potentially negating calorie-burning benefits. Always consult a doctor, especially if you have underlying health conditions.

You may burn slightly more calories exercising in the cold because your body expends energy to maintain its temperature. The colder temperature also helps your body regulate heat better, which can allow you to exercise longer and potentially burn more total calories over the duration of the workout.

Safe ways to activate brown fat include taking cold showers for short durations, lowering your thermostat by a few degrees, or taking a brisk walk outside in cooler weather. Gradually increase your cold exposure to allow your body to adapt safely.