Background: Body adiposity index [BAI], which is based on the measurements of hip circumference and height, has been
suggested as an alternative adiposity index to body mass index [BMI]. Previous studies have demonstrated that BAI exhibits good cross-sectional agreement with percent body fat [PBF].
Objective: To compare BAI with BMI and their correlations with PBF and to define the optimal BAI cut-offs for defining
obesity in rural Thai adults using PBF as a gold standard.
Materials and Methods: A total of 180 men and 254 women aged 20 years or older were recruited using a stratified clustering sampling method. PBF was measured using dual energy x-ray absorptiometry, and the “gold standard” for defining obesity was PBF greater than 25% in men and greater than 35% in women. BMI was obtained by dividing weight (in kg) by height2 (in meters), while BAI was calculated using the following equation: (hip circumference (in centimeters)/height1.5 (in meters)) -18.
Results: The prevalence of PBF-based obesity in men and women was 7.8% and 42.1%, respectively. When using a BMI cutoff of greater than 25 kg/m2, 13.9% of men and 37.4% of women were classified as obese. There was a strong correlation between BAI and BMI (r = 0.76 in men and 0.83 in women, p<0.001). A strong correlation was also found between BMI and PBF (r = 0.71 in men and 0.78 in women, p<0.001), which was comparable with the correlation between BAI and PBF (r = 0.65 in men and 0.73 in women, p<0.001). BAI was a significant predictor of PBF, such that in men, a BAI of at least 29.2 predicted a PBF of 25% (with sensitivity of 85.7% and specificity of 89.8%), while a BAI of at least 32.7 corresponded to a PBF of 35% (with sensitivity of 80.4% and specificity of 88.4%) in women. The area under the receiver operating characteristic curve for BAI in the diagnosis of obesity was approximately 0.85 in both men and women.
Conclusion: Both BMI and BAI are reasonably useful indicators of obesity. We proposed BAI cut-off values for diagnosing obesity of 29.2 in men and 32.7 in women.

Keywords: Body adiposity index, BAI, Body mass index, Obesity, Thai populations