Physical Activity is Associated with Percent Body Fat and Body Composition but not Body Mass Index in White and Black College Students

The objective of this study was to examine the association of self-reported physical activity (PA) with body composition in 290 college students (49% male, 60% White) 18–25 years of age. Outcome measures included: self-reported PA levels calculated in MET-hrs·wk(−1) from the International Physical Activity Questionnaire (IPAQ); body mass index (BMI; in kg·m(−2)); and body composition variables estimated by dual-energy X-ray absorptiometry (DXA). Mean activity levels of the sample were 39.8 ± 23.8 MET-hrs·wk(−1). Participants were divided into quartiles of PA levels: ≥0 to <24.0, ≥24.0 to <34.0, ≥34.0 to <51.25, and ≥51.25 MET-hrs ·wk(−1) and body composition variables were compared by group. Chi-square analyses revealed a significant difference for gender by PA quartile [χ(2) (3, N=290) = 32.42, p < 0.0001], and for gender by race by PA quartile [χ(2) (9, N=290) = 37.82, p < 0.0001]. MET-hrs·wk(−1) was inversely correlated with %BF (r = −0.40, p < 0.0001) but not BMI (r = 0.05, p = 0.43). When comparing body composition variables across PA quartiles, no significant differences were observed for BMI; however, subjects in the highest quartile of PA had a lower percent body fat (%BF) and fat mass (FM), and a higher lean-tissue mass (LTM) compared to subjects in the other three groups. In this cohort of young adults, participants in the highest activity group had a more fit body composition profile (e.g., lower %BF, lower FM, and higher LTM) which was not reflected in BMI and was independent of gender and race.