Associations of body adiposity index, waist circumference, and body mass index in young adults

Background & aims: The Body Adiposity Index (BAI) is an anthropometric measure developed to estimate body composition in field settings. Although this novel measure has been validated against clinical measures of adiposity (%Fat), the relative accuracy of other anthropometric measures, such as Body Mass Index (BMI), and waist circumference (WC), have not been assessed in comparison to the BAI using a 4 compartment (4C) model. Purpose: The primary aim of this study was to examine the association between BMI, WC, BAI, and %Fat in young adults, and determine the relative accuracy of each anthropometric measure when predicting % Fat. Methods: BMI, WC, and BAI were assessed in a sample of young adults (n = 188, 48.4% female, 21.8 +/- .8 years). %Fat assessed using the 4C model was derived from underwater weighing for body density, dual energy X-ray absorptiometry for bone mineral content, and bioimpedance spectroscopy for total body water. Bivariate associations were assessed using Pearson's r, with the relative accuracy of each measure assessed using multivariate linear regression and compared using Akaike's information criterion, R-2 and Delta R-2 statistics. Results: BMI, WC, and BAI were associated with %Fat (r = 0.192, 0.194, and 0.668, respectively, all p <.01). WC and BAI collectively explained 46.3% of the variation in %Fat, and removing BAI significantly reduced model fit (p < .001). When stratified by sex, BAI provided greater accuracy when predicting %Fat beyond WC in men (Delta R-2 = 2.6%, p = .022), but not women (Delta R-2 = 2.1%, p = .078). Conclusion: WC and BAI are more strongly associated with %Fat as measured by the 4C model than BMI in young adults. (C) 2018 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.