Comparison of Body Adiposity Index (BAI) and Body Mass Index (BMI) with Estimations of % Body Fat in Clinically Severe Obese Women

Body Adiposity Index (BAI), a new surrogate measure of body fat (hip circumference/[height(1.5) -18]), has been proposed as an alternative to BMI. We compared BAI with BMI, and each of them with laboratory measures of body fat-derived from bioimpedance analysis (BIA), air displacement (ADP), and dual-energy x-ray absorptiometry (DXA) in clinically severe obese (CSO) participants. Nineteen pre-bariatric surgery CSO, non-diabetic women were recruited (age=32.6±7.7 SD; BMI=46.5±9.0 kg/m(2)). Anthropometrics and body fat percentage (% fat) were determined from BIA, ADP, and DXA. Scatter plots with lines of equality and Bland-Altman plots were used to compare BAI and BMI with % fat derived from BIA, ADP, and DXA. BAI and BMI correlated highly with each other (r=0.90, p<0.001). Both BAI and BMI correlated significantly with % fat from BIA and ADP. BAI, however, did not correlate significantly with % fat from DXA (r=0.42, p=0.08) whereas BMI did (r=0.65, p=0.003). BMI was also the single best predictor of % fat from both BIA (r(2)=0.80, p<0.001) and ADP (r(2)=0.65, p<0.001). The regression analysis showed that the standard error of the estimate (SEE) or residual error around the regression lines was greater for BAI comparisons than for BMI comparisons with BIA, ADP, and DXA. Consistent with this, the Bland and Altman plots indicated wider 95% confidence intervals for BAI difference comparisons than for BMI difference comparisons with their respective means with BIA, ADP, and DXA. Thus, BAI does not appear to be an appropriate proxy for BMI in clinically severe obese (CSO) women.