Relative accuracy of body adiposity index and relative fat mass in participants with and without down syndrome

Background/Objectives: The body adiposity index (BAI) and relative fat mass (RFM) are anthropometric measures developed to estimate body composition (%Fat). There is limited research validating these methods of body composition assessment in adults with Down syndrome (DS). The aim of this study was to examine the accuracy of the BAI and RFM in a sample of adults with- and without DS. We hypothesize that the RFM would provide greater accuracy than the BAI when estimating %Fat. Subjects/Methods: BAI and RFM were assessed in a sample of adults (n = 235, 50.2% female, 20.0% DS, 23.1 ± 6.7 years). %Fat assessed using dual-energy X-ray absorptiometry served as the criterion method of body composition. Between-group differences were assessed using a two-way (SEX × DS) analysis of variance. Results: BAI overestimated %Fat in men without DS, but underestimated %Fat in women without DS (4.1 ± 4.5%Fat vs. −3.5 ± 4.6%Fat, respectively, p \u3c 0.001). BAI overestimated %Fat in men and women with DS (4.7 ± 7.8%Fat vs. 0.8 ± 7.5%Fat, respectively, p = 0.090). RFM slightly overestimated %Fat in male and female participants without DS, and did not vary by sex (0.9 ± 4.0%Fat vs. 0.2 ± 4.2%Fat, respectively, p = 0.248). RFM underestimated %Fat in men and women with DS, with no differences observed between sexes (−2.1 ± 5.3%Fat vs. −2.2 ± 6.9%Fat, respectively, p = 0.953). Conclusions: The BAI and RFM can be used to estimate body composition in individuals with- and without DS, however, the RFM yields greater accuracy and is recommended when more advanced methods of body composition assessment are unavailable or create unwanted participant burden