The effect of a 3-month moderate-intensity physical activity program on body composition in overweight and obese African American college females

Summary: This study evaluated body composition outcomes following a 3-month exercise program for overweight/obese Black women. BMI decreased over the 3-month study despite an observed increase in body fat. Enhancements in bone marrow density and muscle density were also observed. Results show promising yet hypothesis-generating findings to explore in future research.

Introduction: Few studies have evaluated the relationship between aerobic physical activity (PA) and body composition among young adult overweight/obese African American (AA) women.

Purpose: The current study evaluated the effect of a 3-month moderate-intensity aerobic physical activity intervention for overweight and obese young adult women on bone, lean, and fat mass.

Methods: Participants (n = 15) were a randomly selected subset of AA female college students (M age = 21.7 years; M BMI = 33.3) enrolled in a larger PA promotion pilot study (n = 31). Study protocol required participants to engage in four 30–60-min moderate-intensity aerobic PA sessions each week. Whole body composition was measured by dual-energy X-ray absorptiometry (DXA), and peripheral quantitative computed tomography (pQCT) was used to assess additional quantitative and qualitative assessment of the radius.

Results: BMI decreased over the duration of the study (P =.034), reflected by a marginal decrease in body weight (P =.057). However, unexpectedly, increases in adipose tissue measures were observed, including total body fat (P =.041), percent body fat (P =.044), trunk fat (P =.031), and percent trunk fat (P =.041). No changes in DXA-measured bone outcomes were observed (i.e., bone mineral density, P =.069; bone mineral content, P =.211). Results from the pQCT assessment showed that bone marrow density increased (P =.011), but cortical density remained stable (P =.211). A marginally significant increase in muscle density (P =.053) and no changes in muscle area (P =.776) were observed.

Conclusions: A 3-month moderate-intensity PA program was associated with several promising findings, including increased bone marrow and stabilization of body weight. However, the increase in adipose tissue and trend for decreased bone mineral density were unexpected and indicate the need for future studies with larger samples to further explore these outcomes.