The body mass index (BMI) is a useful tool to measure weight adjusted for height (kg/m 2 ) but has a limited ability to identify other variables specific to the individual's unique composition, which can lead to misconceived inferences about the body composition of individuals with similar BMI values. One way to ascertain these variables is through dual-energy x-ray absorptiometry (DXA) which measures bone mineral content (BMC) and bone mineral density (BMD), among other variables. PURPOSE: The objective of this study was to analyze some of the qualities of bones, specifically BMC and BMD, and their relation to the measured BMI of university club sport athletes. METHODS: DXA and BMI data from a larger study of university club sport athletes were utilized. BMI information was calculated using the measured values of height and weight, while BMC and BMD were measured via a whole-body DXA scan (Hologic's Horizon-W) following the manufacturer's instructions. Independent t-tests were used to analyze the information between sexes. RESULTS: Data from 119 club sport athletes (45 female, 74 male) across 15 sports revealed statistically significant differences in BMD (p < .001) and BMC (p < .001) between men and women, despite their BMI being similar (p = 0.471). The BMI for females (24.3 ± 3.7 kg/m 2 ) and males (24.7 ± 3.2 kg/m 2 ) were similar even though women had a smaller mass (66.0 ± 13.5 kg) than men (79.2 ± 11.8 kg; p<.001). Males had significantly greater (p < .001) BMC (2.97 ± 0.37 kg vs 2.25 ± 0.37 kg) and BMD (1.28 ± 0.09 g/cc vs 1.17 ± 0.08 g/cc) compared to females. Interestingly, the lowest and highest team BMD values occurred in the same sport; female gymnasts had the lowest team BMD (1.13 ± 0.06 g/cc) while male gymnasts had the highest team BMD (1.32 ± 0.09 g/cc).
CONCLUSION: BMI can be a practical tool for identifying weight categories; however, it should not be used to make inferences about BMD and BMC, regardless of similarities between the BMI results of individuals of opposite sexes.