Brown adipose tissue, anthropometric traits, and metabolic profiles in women with normal weight obesity.

Emerging evidence indicates that individuals with normal-weight obesity (NWO), characterized by a normal body mass index (BMI) but high body fat (BF) percentage, are at increased risk of cardiometabolic diseases. Brown adipose tissue (BAT) is crucial for cardiometabolic health. However, the connection between adipose tissue density and NWO remains elusive. A total of 90 women aged 30-59 with BMIs ranging from 18.5 to 32 were investigated. We measured BAT vascular density as the total hemoglobin concentration using near-infrared time-resolved spectroscopy (NIR-TRS). While the total, visceral, and subcutaneous fat areas were significantly higher in the NWO group than those in the normal-weight group, the BAT vascular density was significantly lower in the NWO group (49.83, 95% CI: 45.98, 53.67) than that in the normal-weight group (64.94, 95% CI: 57.71, 72.17) (p < 0.01). Multivariate regression analysis identified BAT vascular density as a significant predictor of BF percentage (β = -0.308, p < 0.001). These findings suggest that women with NWO have markedly lower BAT vascular densities than those exhibited by women in the normal-weight group, underscoring the remarkable association of BAT with BF accumulation and the development of obesity and cardiometabolic dysregulation.