Cold exposure enhances fat utilization but not non-esterified fatty acids, glycerol or catecholamines availability during submaximal walking and running.
Level 3 - non-randomized controlled study
Controlled crossover laboratory trial in humans with randomization not explicitly stated in the abstract
PubMed 23675353 · doi:10.3389/fphys.2013.00099
What was done
Ten lightly clothed male participants performed 60-minute walking (at 50% VO2max) and running (at 70% VO2max) bouts in a climatic chamber at 0°C or 22°C while core temperature and oxygen consumption were maintained. Thermal, cardiovascular, and oxidative parameters were measured every 15 minutes. Blood samples were drawn pre-exercise and at 30 and 60 minutes to measure non-esterified fatty acids (NEFAs), glycerol, glucose, beta-hydroxybutyrate, lipids, and catecholamines.
What was found
Skin temperature and heart rate were lower during cold trials, whereas core temperature remained unchanged. Cold exposure increased fat utilization, showing a lower respiratory quotient (-0.03 ± 0.02), increased fat oxidation (+0.14 ± 0.13 g · min⁻¹), and greater contribution of fat to energy expenditure (+1.62 ± 1.99 kcal · min⁻¹). No significant differences between cold and control trials were found for blood NEFAs, glycerol, glucose, beta-hydroxybutyrate, or catecholamines.
Why it matters
This indicates that cold-induced increases in fat oxidation during walking and running occur independently of changes in systemic catecholamines or circulating fatty acid availability, pointing toward local intramuscular triglyceride use.
Limits
The sample size was very small (10 males), limiting generalizability to females and broader populations. The abstract does not specify whether trials were randomized, and intramuscular lipids were not directly measured via muscle biopsy.
Cited by
- supports Combining cold stress with a calorie-restricted diet shifts the respiratory quotient (RQ) toward 0.7, indicating a shift toward fat oxidation.