Cold Exposure and Metabolism
Two-hour cold exposure at 17°C increases energy expenditure by 93 kcal in BAT-positive men (Ouellet 2012). BAT accounts for ~22% of cold thermogenesis; total cold-induced metabolic rate elevation is 1.8–2.5× resting during moderate cold.
| Measure | Value | Unit | Notes |
|---|---|---|---|
| Energy expenditure increase (17°C, 2h) | 93 | kcal | Ouellet 2012; in BAT-positive men; above resting baseline |
| BAT contribution to cold thermogenesis | ~22 | % of cold-induced energy expenditure | Ouellet 2012; remaining ~78% from shivering and other tissues |
| Metabolic rate during moderate cold exposure | 1.8–2.5× | above resting | 17–20°C ambient; shivering contributing |
| BAT glucose uptake (cold-activated) | 12× | vs thermoneutral | Per gram of tissue; highest glucose-consuming tissue during cold |
| Blood glucose change during cold | ↓ Moderate | Glucose consumed by BAT and shivering muscle; modest acute reduction | |
| FFA mobilization during cold | Significant increase | Lipolysis activated by NE; free fatty acids fuel both BAT and shivering | |
| Metabolic adaptation (3-week cold acclimation) | +30–40% BAT capacity | Blondin 2014: cold acclimatization increases BAT oxidative capacity |
Cold exposure is one of the few environmental stimuli that measurably increases metabolic rate without exercise. Understanding the magnitude, sources, and adaptations of cold-induced thermogenesis helps contextualize how cold exposure fits into metabolism and energy balance.
Total Energy Expenditure During Cold
Cold exposure increases energy expenditure through multiple parallel mechanisms:
| Mechanism | Contribution | Notes |
|---|---|---|
| Brown adipose tissue (BAT) | ~22% | Ouellet 2012; requires BAT-positive subjects |
| Shivering (skeletal muscle) | ~40–60% | Dominant in cold-naive individuals |
| Muscle tone increase (pre-shivering) | ~15% | Subtle muscle contraction without overt shivering |
| Increased heart rate, breathing | ~5% | Cardiovascular thermogenic cost |
| Other (liver, organs) | ~10% | Hepatic glucose production, organ heat |
These proportions shift with cold acclimatization: BAT and non-shivering thermogenesis contribute more; shivering contributes less.
The Ouellet 2012 Study
Ouellet and colleagues used a combination of ¹⁸F-FDG PET-CT (for BAT glucose uptake) and whole-body indirect calorimetry (for total energy expenditure) in men with confirmed BAT:
| Condition | Energy Expenditure | BAT Glucose Uptake |
|---|---|---|
| Thermoneutral (30°C) | Baseline | Minimal |
| Cold (17°C, 2 hours) | +93 kcal vs baseline | 12× increase per gram |
BAT accounted for 22% of the cold-induced thermogenesis increment. Shivering and increased muscle tone accounted for most of the remainder.
Glucose and Lipid Metabolism During Cold
Cold exposure profoundly alters substrate utilization:
Glucose:
- BAT becomes a major glucose sink (12× uptake per gram)
- Shivering muscle consumes glycogen rapidly
- Blood glucose modestly decreases during 2-hour cold exposure
- Insulin sensitivity acutely improves during cold (mechanistically linked to BAT glucose uptake)
Fatty acids:
- Norepinephrine activates hormone-sensitive lipase in white adipose tissue
- Free fatty acids (FFA) mobilized into circulation
- FFA are the primary fuel for sustained BAT thermogenesis (glycogen runs out; lipids continue)
- Intramyocellular lipid contributes to prolonged shivering (Blondin 2014)
Metabolic Adaptation with Regular Cold Exposure
Blondin et al. (2014) studied men before and after 4 weeks of cold acclimation (controlled cool room exposure for 2 hours/day at 10°C). Post-acclimatization:
- BAT oxidative capacity increased 30–40%
- Shivering intensity decreased for equivalent cold stress
- Non-shivering thermogenesis proportion increased
This shift from shivering to non-shivering thermogenesis is the hallmark of metabolic cold adaptation — the body becomes more efficient at generating heat without gross muscle contraction.
Practical Caloric Impact
| Protocol | Duration | Estimated Extra Energy |
|---|---|---|
| Cold shower (15–20°C) | 1–2 min | ~5–10 kcal |
| Ice bath (12°C) | 15 min | ~30–50 kcal |
| Cold room (17°C) | 2 hours | ~50–100 kcal |
| Winter swimming (near freezing) | 10–20 min | ~40–80 kcal |
These numbers are meaningful but modest — cold exposure is not a primary weight loss tool. Its metabolic value lies in BAT activation and insulin sensitivity improvement, not raw caloric expenditure.
Related Pages
Sources
- Ouellet V et al. (2012) — Brown adipose tissue oxidative metabolism contributes to energy expenditure during acute cold exposure in humans. J Clin Invest
- van Marken Lichtenbelt WD et al. (2009) — Cold-activated brown adipose tissue in healthy men. N Engl J Med
- Blondin DP et al. (2014) — Increased brown adipose tissue oxidative capacity in cold-acclimated humans. J Clin Endocrinol Metab
- Iwen KA et al. (2017) — Cold-induced effects on glucose metabolism in brown fat and muscle. J Physiol