Cold acclimation recruits human brown fat and increases nonshivering thermogenesis.
Level 4 - case-series / case-control
Uncontrolled before-and-after physiological interventional study in humans
PubMed 23867626 · doi:10.1172/JCI68993
What was done
Human subjects underwent a 10-day cold acclimation protocol to evaluate changes in brown adipose tissue (BAT) activity and nonshivering thermogenesis (NST). Investigators assessed sex differences, measured cellular respiration in permeabilized muscle fibers and isolated mitochondria, analyzed abdominal subcutaneous white adipose tissue biopsies for cell-specific markers and uncoupling protein-1 (UCP1) to detect beige/brite recruitment, and tracked subjective thermal comfort and shivering.
What was found
The 10-day cold acclimation protocol increased BAT activity in parallel with an increase in NST, with no sex differences observed before or after acclimation. Skeletal muscle mitochondrial uncoupling showed no significant contribution to the NST increase. Cold acclimation did not induce browning of abdominal subcutaneous white adipose tissue based on UCP1 and cell markers. Subjectively, participants rated the cold environment as warmer, reported feeling more comfortable, and experienced less shivering. The abstract reports no quantitative numerical values or effect sizes.
Why it matters
This study demonstrates that repeated moderate cold exposure can recruit human brown adipose tissue and enhance nonshivering energy expenditure without requiring skeletal muscle mitochondrial uncoupling or subcutaneous fat browning.
Limits
The abstract does not state the sample size, exact participant characteristics, cold exposure temperature/duration specifics, or quantitative numerical results (p-values, fold changes). There was no non-cold control group described to rule out time-dependent confounding.
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