Active Brown Adipose Tissue Is Associated With a Healthier Metabolic Phenotype in Obesity

Abstract

Obesity is associated with increasing cardiometabolic morbidity and mortality rates worldwide. Not everyone with obesity, however, develops metabolic complications. Brown adipose tissue (BAT) has been suggested to be a promoter of leanness and metabolic health. To date, little is known about the prevalence and metabolic function of BAT in people with severe obesity, a population at high cardiometabolic risk. In this cross-sectional study, we included 40 individuals with World Health Organization class II-III obesity (BMI ≥35 kg/m2). Using a 150-min personalized cooling protocol and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography, cold-activated BAT was detectable in 14 of the participants (35%). Cold-induced thermogenesis was significantly higher in participants with detectable BAT compared with those without. Notably, individuals with obesity and active BAT had 28.8% lower visceral fat mass despite slightly higher total fat mass compared with those without detectable BAT 18F-FDG uptake. The lower amount of visceral fat mass was accompanied by lower insulin resistance and systemic inflammation and improved nonalcoholic fatty liver disease parameters, all adjusted for age, sex, and percent body fat. Contrary to previous assumptions, we show here that a significant fraction of individuals with severe obesity has active BAT. We found that decreased BAT 18F-FDG uptake was not associated with adiposity per se but with higher visceral fat mass. In summary, active BAT is linked to a healthier metabolic phenotype in obesity.