Obesity in children is becoming a global issue. Lower cold-induced brown adipose tissue (BAT) activity had been associated with obesity and metabolic dysfunction in adults, but the same cannot be said for youngsters. For a study, researchers used MRI to assess cold-induced supraclavicular (SCV) BAT activity (% change in proton density fat fraction [PDFF]) within the SCV area following 1 h of whole-body cold exposure (18°C) in 26 boys aged 8–10 years: 13 with normal BMI and 13 with overweight/obesity. In addition, anthropometry, body composition, hepatic fat, visceral adipose tissue (VAT), and pre-and post-cold PDFF of the subcutaneous adipose tissue (SAT) were all assessed in the posterior neck and abdomen. 

When compared to boys with a normal BMI, those with overweight/obesity exhibited a smaller cold-induced percent drop in SCV PDFF (1.6±0.8 vs. 4.7±1.2%, P=0.044). SCV PDFF decreased in boys with a normal BMI (2.7±0.7%, P=0.003) but not in those who were overweight or obese (1.1±0.5%, P=0.053). There were no cold-induced changes in the PDFF of neck SAT (-0.89± 0.7%, P=0.250; 0.37± 0.3%, P=0.230) or abdomen SAT (-0.39± 0.5%, P=0.409; 0.25 0.2%, P=0.139, for normal BMI and overweight/obesity groups, respectively). BMI (r=-0.39, P=0.047), waist circumference (r=-0.48, P=0.014), and VAT (r=-0.47, P=0.014) were all negatively associated with the cold-induced percent drop in SCV PDFF. BAT activity was lower in persons with overweight/obesity in both young boys and adults, suggesting that restoring exercise may be crucial for improving metabolic health.