OBJECTIVE: To evaluate the association between objectively measured daily physical activity and body fat. STUDY DESIGN: Cross-sectional, observational, study of 248 children aged 7.9 to 11.1 years. Abdominal fat mass and total body fat mass were measured by dual-energy X-ray absorptiometry. Daily physical activity was assessed by accelerometers for 4 days. RESULTS: Total body fat expressed as a percentage of body mass was inversely related to minutes of vigorous physical activity per day, for all children r = -0.38 (P