Technical Abstract: The influence of moderate-to-vigorous physical activity (MVPA) and general versus central adiposity on pediatric metabolic risk is not well described. We conducted a secondary analyses on pediatric participants from the National Health and Nutrition Examination Survey, 2003–2006 (n=2,155). MVPA (min/day) and adherence to MVPA recommendations were assessed objectively by accelerometers. Body mass index (BMI) z-score and waist circumference (WC) were measured by standard protocols. The main dependent variables included an overall metabolic risk score and clinical tests related to metabolic risk. A series of linear regression analyses were used to examine BMI z-score versus WC as a mediator of the relationship between MVPA and the metabolic risk score or the individual components, controlling for sociodemographic covariates. All analyses with BMI z-score as an independent variable controlled for WC and vice versa. The product-of-coefficients method was used to test for mediation. Our results showed that MVPA adherence was inversely associated and WC was positively associated with the metabolic risk score. Our conclusions are that MVPA correlated with pediatric metabolic risk and this relationship was mediated by central adiposity for CRP and HDL-C. This finding suggests the need for programs to screen for and improve children's MVPA and WC.