Ectopic Fat distribution and adverse muscle composition in South Asians: Findings from the UK biobank.

Background: South Asians (SA) have higher risk of cardiometabolic disease compared to other ethnicities. However, detailed analyses of body compositional profile (BCP) in large cohorts with inclusion of ectopic fat depots and muscle composition is lacking. Methods: Using MRI data from UK biobank, we compared body compositional data in South Asians (n = 397) relative to age, sex, height, and weight-matched white Europeans (EUR) (matched 5:1 to SA group). We also compared BCP in 66 SAs with type 2 diabetes (T2D) versus matched EUR (matched 3:1 to SA group). Results: SAs had higher overall levels of fat compared to EUR (mean difference in: visceral adipose tissue 0·20 L; subcutaneous adipose tissue 0·93 L; liver fat 0·92 pp; muscle fat infiltration (MFI) 0·59 pp, all p < 0·001) and lower muscle volume (mean difference -0·61 L, p < 0·001) (all adjusted for sex, age, height, and weight). The higher MFI and lower muscle volume resulted in a higher prevalence of adverse muscle composition in the SA group (19·9 % vs 7·9 %). Differences remained significant with further adjustment for lifestyle and socioeconomic factors. Notably, SA participants with T2D had similar BCP to sex-, age-, height-, and weight-matched EUR participants with T2D. Conclusion: SAs have greater visceral, liver, and muscle fat accumulation, but lower muscle volume compared to EUR. These findings may underlie their greater risk for T2D and atherothrombotic outcomes. Lifestyle changes to prevent or reduce weight gain can help offset cardiometabolic risks in SAs by facilitating favorable changes in body composition.