Effect of cold exposure on fuel utilization in humans: plasma glucose, muscle glycogen, and lipids.
Level 3 - non-randomized controlled study
Non-randomized before-and-after physiological intervention study in humans.
PubMed 12070189 · doi:10.1152/japplphysiol.00773.2001
What was done
Indirect calorimetry combined with stable isotope methodology ([U-13C]glucose ingestion) was used to quantify substrate oxidation rates in men acutely exposed to cold for 2 hours via a liquid-conditioned suit perfused with 10°C water.
What was found
Cold exposure increased heat production by 2.6-fold. Oxidation rates increased for plasma glucose from 39.4 ± 2.4 to 93.9 ± 5.5 mg/min (+138%), for muscle glycogen from 126.6 ± 7.8 to 264.2 ± 36.9 mg glucosyl units/min (+109%), and for lipids from 46.9 ± 3.2 to 176.5 ± 17.3 mg/min (+376%). Total heat production was derived 50% from lipids, 30% from muscle glycogen, 10% from plasma glucose, and 10% from proteins, with muscle glycogen providing 75% of total carbohydrate oxidized.
Why it matters
Quantifies the human metabolic fuel mix during cold-induced shivering, demonstrating that lipids and muscle glycogen furnish the vast majority of thermogenic energy rather than circulating glucose.
Limits
The abstract does not state the sample size (n). The study tested only men during a brief 2-hour exposure, limiting generalizability to women, different shivering intensities, or prolonged cold acclimatization.
Cited by
- contradicts Shivering burns carbohydrate as fuel rather than fat.