Cold-activated brown adipose tissue in healthy men.
Level 3 - non-randomized controlled study
Non-randomized physiological controlled study comparing lean and overweight/obese cohorts under controlled temperature exposures.
PubMed 19357405 · doi:10.1056/NEJMoa0808718
What was done
Researchers evaluated 24 healthy men (10 lean with BMI < 25, and 14 overweight or obese with BMI ≥ 25) to determine the presence, distribution, and activity of brown adipose tissue (BAT). Participants were examined under thermoneutral conditions (22°C) and during mild cold exposure (16°C). BAT activity was measured using integrated 18F-fluorodeoxyglucose positron-emission tomography and computed tomography (18F-FDG PET-CT), body composition via dual-energy x-ray absorptiometry (DEXA), and energy expenditure via indirect calorimetry.
What was found
BAT activity was detected in 23 of the 24 participants (96%) during cold exposure, but was undetectable under thermoneutral conditions. BAT activity was significantly lower in overweight or obese men compared to lean men (P = 0.007). In addition, BAT activity correlated negatively with BMI and body fat percentage, and correlated positively with resting metabolic rate.
Why it matters
This study provided definitive evidence that functional brown adipose tissue is prevalent and cold-inducible in adult humans, rather than restricted to infants, while establishing that its activity is blunted in obesity.
Limits
The study had a small sample size (n = 24) and included only young male participants, limiting generalizability to women and older demographics. Long-term metabolic outcomes were not evaluated.
Cited by
- supports Individuals who possess higher amounts of brown adipose tissue burn more energy and demonstrate better metabolic function.