Can Cold Exposure Help You Burn More Calories?
Yes. This meta-analysis of 10 randomized controlled trials found that acute cold exposure increases energy expenditure, at a rate equal to about 188 calories a day while people are exposed. Cold also activates brown adipose tissue (brown fat), which burns calories to generate heat.
Researchers from Jilin University in China analyzed studies on cold exposure and metabolism. They found that even brief cold exposure at temperatures of 16-19°C significantly increased both energy burning and brown fat activity in healthy adults. This has important implications for fighting obesity.
Dr. Kumar’s Take
This meta-analysis suggests that cold exposure increases metabolism while you are cold. The 188 calories per day figure is a rate measured during exposures that lasted from 30 minutes to 12 hours, so a short cold spell adds only a fraction of that. The brown fat activity result rests on just two studies that disagreed a fair amount with each other. What’s particularly interesting is that cold activates brown fat, which is the specialized fat tissue that burns calories for heat rather than storing them. While cold exposure isn’t a magic weight loss solution, it does appear to boost calorie burning through multiple mechanisms.
What the Research Shows
The meta-analysis included 10 randomized controlled trials from Finland, the United States, Australia, Switzerland, the Netherlands, and Japan. Participants were mostly healthy adults aged 20-40 years.
Energy expenditure: Cold exposure at 16-19°C increased calorie burning compared to room temperature (24°C), at a rate equal to about 188 calories a day while people were exposed (p < 0.05). The exposures lasted from 30 minutes to 12 hours.
Brown fat volume: Significantly increased after cold exposure (p < 0.05).
Brown fat activity: Improved after cold exposure (p = 0.04).
Fatty acid uptake: Brown fat absorbed more fat from the bloodstream during cold exposure (p < 0.05).
How Brown Fat Works
Brown adipose tissue (BAT) is different from regular white fat:
White fat: Stores excess calories as fat.
Brown fat: Burns calories to generate heat (thermogenesis).
Brown fat contains many mitochondria, the energy factories in cells. When activated by cold, these mitochondria burn fat and glucose to produce heat instead of storing them. A protein called UCP1 makes this possible by short-circuiting the normal energy-production process to generate heat.
Who Has More Brown Fat?
Brown fat activity varies by:
- Age: More than 50% of people aged 20-29 have detectable brown fat, but less than 10% of those over 50
- Body weight: Higher activity in normal-weight people than in overweight or obese individuals
- Season: More brown fat detected in winter than summer
- Sex: Some studies suggest differences between men and women
The Limits of Cold Exposure
While the findings are exciting, some important caveats exist:
Short-term vs. long-term: This meta-analysis focused on acute cold exposure. Chronic exposure doesn’t always produce the same benefits.
Compensatory eating: Prolonged cold stimulation often increases food intake, which can offset the extra calorie burning.
Practical limitations: Unlike mice, humans protect themselves from cold, keeping brown fat activity lower than laboratory conditions might suggest.
No weight loss shown: Increased calorie burning and decreased fat mass have been observed, but actual weight loss hasn’t been consistently demonstrated.
Practical Takeaways
- Cold exposure (16-19°C) raised calorie burning at a rate equal to about 188 calories a day while people were exposed
- Cold activates brown fat, which burns calories to generate heat
- The effect is stronger in younger, leaner individuals
- Cold exposure alone probably won’t cause significant weight loss
- Combining cold exposure with exercise and diet may be more effective
Related Studies and Research
- Related Podcast Episode
- Cold Water Swimming: Benefits and Risks (narrative review)
- Does the Trigeminal Cardiac Reflex Affect Blood Flow to the Brain?
FAQs
How cold does it need to be to activate brown fat?
The studies in this meta-analysis used temperatures of 16-19°C (61-66°F), which is cool but not extremely cold. This is significantly below the typical room temperature of 24°C (75°F).
Can cold exposure help me lose weight?
Cold exposure increases calorie burning and decreases fat mass, but studies haven’t consistently shown actual weight loss. This may be because people eat more to compensate for the extra energy burned.
Does everyone have brown fat?
Most young adults have detectable brown fat, but brown fat activity falls with age and is lower in people with a higher BMI or more body fat. Fewer than 10% of people over 50 show detectable brown fat on scans.
Bottom Line
This meta-analysis of 10 randomized controlled trials suggests that acute cold exposure increases energy expenditure and activates brown adipose tissue in healthy adults. Cold exposure at 16-19°C boosted calorie burning at a rate equal to about 188 calories a day while people were exposed, and increased brown fat volume and activity. Brown fat burns calories to generate heat, making it a potential target for obesity treatment. However, cold exposure alone hasn’t been shown to produce significant weight loss, likely because people compensate by eating more. The most practical approach may be combining brief cold exposure with other lifestyle interventions.
