The body adiposity index fails to predict body fat in Costa Rican college students

Abstract

Purpose: The study was designed to verify the validity of BAI in predicting %BF in a sample of Costa Rican college students, using dual-energy X-ray absorptiometry (DEXA) as the reference method. Methods: Volunteers were 199 participants (Mean age = 18.9 ± 2.6 yrs.). DEXA was used as the “gold standard” to determine %BF. Pearson’s correlation coefficient was used to evaluate the association between BAI and %BF assessed by DEXA. A paired sample t-test was used to test differences in mean %BF obtained with BAI and DEXA methods. To evaluate the concordance between %BF measured by DEXA and estimated by BAI, we used the Lin’s concordance correlation coefficient and the agreement analysis of Bland-Altman. Results: The correlation between % BF obtained by DEXA and that estimated by BAI was r = 0.73, p < 0.001. Paired t-test showed a significant mean difference in %BF between methods (BAI = 26.9 ± 4.5% vs. DEXA 28.7 ± 11.0; p = 0.002). The bias of the BAI was 1.8 ± 8.3 %BF (95% CI = 0.65 to 2.97), indicating that the BAI method measured lower %BF than the DEXA. Lin’s concordance correlation coefficient was considered poor (Cb = 0.68). Finally, the Bland-Altman plot (Figure 1) showed BAI underestimating %BF in relation to the “gold standard”. Conclusions: In Costa Rican college students BAI presented low agreement with %BF measured by DEXA; therefore, BAI is not recommended for %BF prediction in this Central American sample studied.