Physical Activity and Body Composition: A 20-Month Prospective Study of Middle-Age Women

Objective: To determine the extent that physical activity accounts for changes in body composition and body weight over time, independent of dietary intake and other potential confounding factors. Methods and Procedures: A cohort of 256 women ages 35-45 at baseline participated in the study. A prospective design was utilized with baseline and follow up assessments 20-months apart. Primary assessments included body weight, body fat percentage, physical activity assessed by accelerometery, and 7-day weighed diet record. Regression analysis was used to determine the extent to which changes in physical activity contributed to changes in body fat percentage and body weight over the study period. Relative risk for change in body fat and weight was calculated using Poisson regression. Results: Over the study period, there were significant changes in body fat percentage, body weight and physical activity. Change in physical activity was a significant predictor of changes in body fat and body weight over the 20-month study period. The impact of change in physical activity on body weight remained significant after controlling for dietary intake and other potential confounding variables. Those in the lower levels of physical activity also had an increased risk of both weight and fat gain over the study period. Discussion: Based on these results, change in physical activity status is an independent predictor of body fat and body weight change over time. Those who are less active also have increased risk of weight and fat gain over time independent of dietary