Body Composition Predictors of Physical Activity

Rhode, P.C., Morris, D.D., Smith, M.L., Martin, P.D., Brantley, P.J. (2005). Body Composition Predictors of Physical Activity. Proceedings from the Society of Behavioral Medicine’s Twenty-Sixth Annual Meeting. Annals of Behavioral Medicine, 29, S006.

Objective: The purpose of this study was to retrospectively examine the relationship between body composition measured at 12-months on total rates of physical activity over the same 1-year period. Methods: Subjects were obtained from a sample of middle-aged males and females (n = 120). Physical activity was assessed with the Baecke physical activity questionnaire at baseline, 6 and 12-months. Body composition was measured using body mass index (BMI), computerized tomography (CT) and dual-energy X-ray absorptionmetry (DEXA), at baseline and 12-months. Body composition variables were entered into regression models to predict total rates of physical activity from baseline to 12-months. Results: The variance accounted for in each model was surprisingly consistent across each method and measurement of body composition (BMI: r2 = .04, p < .05; total body fat: r2 = .05, p < .03; trunk fat: r2 = .05, p < .02; total adipose tissue: r2 = .05, p < .03; visceral adipose tissue: r2 = .06, p < .01). In addition, baseline analyses of the predictors were non-significant.

Conclusions: The findings from this study suggest that adiposity was significant in predicting physical activity over the past year, but was not a significant predictor of prospective physical activity behavior, indicating that participants who engaged in higher levels of physical activity over the past 12-months had 4%-6% lower rates of adiposity at the end of that same year.

Coach D Notes: This study demonstrated that BMI has nearly the same amount of variance in relation to body composition as did more advanced measures (CT & DEXA) for body composition. This suggests that BMI seems to be an accurate indicator of overweight and obesity for normal, healthy middle-aged males and females. BMI is based on height – weight tables and any trainer here in the club and tell you your BMI. You do not need an expensive analysis to determine if you are within a healthy weight range for your gender and height. However, BMI does not account for difference in type of tissue (lean vs. fat) therefore someone who is really lean/muscular may be listed in the “overweight” range according to BMI measurements. If you feel this is the case for you, ask one of our trainers to measure your body composition using another method. This will determine the ratio of lean tissue to fat tissue that you carry on your body.

For more information about body composition feel free to contact me.