Is BMI Enough? Body Composition Profiles and Cardiometabolic Risk in Hmar Tribe of Northeast India

Body mass index (BMI) is widely used to assess health risk but overlooks fat and lean mass. This limitation is particularly salient for Indigenous/Tribal South Asian populations, who exhibit distinct body composition and cardiometabolic profiles. This study explores the distributions of BMI, fat mass index (FMI), and fat-free mass Index (FFMI) among the Hmar tribe of Northeast India, and evaluates their predictive utility for hypertension, with sex-specific focus.

A cross-sectional study was conducted on 1207 adults (598 men, 609 women) using anthropometry, skinfolds, and bioelectrical impedance. BMI was classified using WHO (1995) and WHO Asia-Pacific (2000) criteria. Polynomial regressions generated sex-specific FFMI and FMI reference ranges. ROC analysis evaluated the predictive utility of BMI, FMI, and FFMI for hypertension.

FFMI/BFMI ranged 16.3-19.2/2.2-5.8 kg/m² (men) and 15.1-17.5/3.5-7.6 kg/m² (women) under WHO cutoffs; narrower under Asia-Pacific: 16.3-18.5/2.2-4.5 (men), 15.1-16.7/3.5-6.3 (women), differing from other populations reflecting ethnic variability. Overweight and/or obesity prevalence increased from 32.06% (WHO, 1995) to 49.96% (WHO, 2000). Despite similar BMI and FFMI across sexes, significant differences were observed in FMI (WHO 1995: χ² = 8.26, p < 0.05; WHO 2000 χ² = 9.46, p < 0.05). Hypertension affected 21% of participants. FFMI emerged as the strongest predictor of hypertension in men (AUC = 0.704), while BMI was more predictive in women (AUC = 0.761).

BMI alone is insufficient for assessing cardiometabolic risk among the Hmars. Sex-specific differences in FMI and FFMI, and their predictive value for hypertension, highlight the need for body composition-based population-sensitive screening strategies.