Validity of simple, novel measures of generalized and central obesity among young Asian Indian women.

OBJECTIVE: The study examined the validity of simple and novel measures of generalized obesity- [body mass index (BMI, kg/m2), fat mass index (FMI, kg/m2), and body fat percent (BF%)] and central obesity--[waist circumference (WC, cm), waist-hip ratio (WHR), and waist-to-height ratio (WC/ht ratio)] against BF% and BMI as criteria. It also aimed to predict fat-free mass index (FFMI, kg/m 2 ), FMI, and BF% ranges for various BMI categories.

DESIGN: Cross-sectional study.

MATERIALS AND METHODS: Weight, BF%, fat mass (FM), and fat-free mass (FFM) were measured using leg-to-leg bioelectrical impedance in 183 women. Height, hip, and waist circumferences were taken using standard methods. The indices [FMI, FFMI, WHR, W/ht ratio] were computed.

RESULTS: The study revealed that FMI, BMI, WC, and WC/ht ratio were highly correlated with BF% (r = 0.978; r = 0.939; r = 0.894; r = 0.890, respectively, P < 0.01), whereas WHR had the least correlation (r = 0.497, P < 0.01). The FMI showed a higher positive predictive value (PPV) in diagnosing generalized obesity compared to BMI with BF% as criterion and higher PPV than BF% with BMI as criterion. Considering only the indices of central obesity, WC was the most predictive in identifying women with high BF% (≥ 30% and ≥ 35%), whereas WC/ht ratio proved to be a better index in identifying women with BMI greater than 23 and 25 kg/m2. The normal BMI for Asians (18.5-23 kg/m 2 ), the at-risk group (23- 25 kg/m2), and the obese class I (25-30 kg/m2) corresponded to FFMI values of 14.1-15.1 kg/m 2, 15.1-15.5 kg/m 2, 15.5-16.1 kg/m 2, respectively, and to FMI values of 4.4-7.9 kg/m 2, 7.9-9.5 kg/m 2, 9.5-13.9 kg/m 2, respectively. The BMI cutoff of 18.5, 23, 25, 27.5, and 30 kg/m 2 corresponded to BF% of 23.6, 34.3, 38.3, 42.6, and 46.3%, respectively.

CONCLUSION: FMI was a better predictor of generalized obesity compared to BMI and BF%. Considering abdominal obesity as an independent risk factor for insulin resistance, both WC and WC/ht ratio were able to predict central obesity better than WHR. Finally, the study presents ranges for FFMI and FMI for various BMI categories.