Adults with metabolically healthy overweight or obesity present more brown adipose tissue and higher thermogenesis than their metabolically unhealthy counterparts

Background: There is a subset of individuals with overweight/obesity characterized by a lower risk of cardiometabolic complications, the so-called metabolically healthy overweight/obesity (MHOO) phenotype. Despite the relatively higher levels of subcutaneous adipose tissue and lower visceral adipose tissue observed in individuals with MHOO than individuals with metabolically unhealthy overweight/obesity (MUOO), little is known about the differences in brown adipose tissue (BAT). Methods: This study included 53 young adults (28 women) with a body mass index (BMI) ¿25 kg/m2 which were classified as MHOO (n = 34) or MUOO (n = 19). BAT was assessed through a static 18F-FDG positron emission tomography/computed tomography scan after a 2-h personalized cooling protocol. Energy expenditure, skin temperature, and thermal perception were assessed during a standardized mixed meal test (3.5 h) and a 1-h personalized cold exposure. Body composition was assessed by dual-energy x-ray absorptiometry, energy intake was determined during an ad libitum meal test and dietary recalls, and physical activity levels were determined by a wrist-worn accelerometer. Findings: Participants with MHOO presented higher BAT volume (+124%, P = 0.008), SUVmean (+63%, P = 0.001), and SUVpeak (+133%, P = 0.003) than MUOO, despite having similar BAT mean radiodensity (P = 0.354). In addition, individuals with MHOO exhibited marginally higher meal-induced thermogenesis (P = 0.096) and cold-induced thermogenesis (+158%, P = 0.050). Moreover, MHOO participants showed higher supraclavicular skin temperature than MUOO during the first hour of the postprandial period and during the cold exposure, while no statistically significant differences were observed in other skin temperature parameters. We observed no statistically significant differences between MHOO and MUOO in thermal perception, body composition, outdoor ambient temperature exposure, resting metabolic rate, energy intake, or physical activity levels. Interpretation: Adults with MHOO present higher BAT volume and activity than MUOO. The higher meal- and cold-induced thermogenesis and cold-induced supraclavicular skin temperature are compatible with a higher BAT activity. Overall, these results suggest that BAT presence and activity might be linked to a healthier phenotype in young adults with overweight or obesity.

The study was supported by the Junta de Andalucía, Consejería de Transformación Económica, Industria, Conocimiento y Universidades Dirección General de Investigación y Transferencia del Conocimiento (ref. P18-RT-4455, ref. SOMM17/6107/UGR, and DOC 01151) and European Regional Development Funds (ERDF), the Spanish Ministry of Economy and Competitiveness via the Fondo de Investigación Sanitaria del Instituto de Salud Carlos III (PI13/01393), and PTA-12264, Retos de la Sociedad (DEP2016-79512-R), the Spanish Ministry of Education (FPU13/04365, FPU15/04059 and FPU19/01609), the Fundación Iberoamericana de Nutrición (FINUT), the Redes Temáticas de Investigación Cooperativa RETIC (Red SAMID RD16/0022), the AstraZeneca HealthCare Foundation, the University of Granada Plan Propio de Investigación 2016 -Excellence actions: Unit of Excellence on Exercise and Health (UCEES). G.SD is supported by a Marie Sklodowska-Curie Actions-Individual Fellowship (101028941; Horizon 2020, European Commission). B.MT is supported by a grant for the requalification of the Spanish university system from the Ministry of Universities of the Government of Spain, funded by the European Union, NextGeneration EU (María Zambrano program, reference RR _C_2021_04). J.M.A.A. is supported by the Juan de la Cierva-Formación Grant FJC2020-044453-I funded by MCIN/AEI/10.13039/501100011033 and 'European Union NextGeneration EU/PRTR'