Physical activity in US youth: effect of race/ethnicity, age, gender, and weight status.

PURPOSE To describe physical activity (PA) levels by race/ethnicity, age, gender, and weight status in a representative sample of US youth. METHODS Cross-sectional data from the 2003-2004 and 2005-2006 National Health and Nutrition Examination Survey were combined and analyzed. Youth aged 6-19 yr with at least four 10-h days of PA measured by accelerometry were included (n = 3106). Outcomes included mean counts per minute and minutes spent in moderate-to-vigorous PA (MVPA). RESULTS Among the groups, the 6- to 11-yr-olds spent more time (88 min·d) in MVPA than the 12- to 15-yr-olds (33 min·d) and 16- to 19-yr-olds (26 min·d; P < 0.001 for both). Females spent fewer minutes per day in MVPA than males (P < 0.001). Overall, obese youth spent 16 fewer minutes per day in MVPA than normal-weight youth. However, non-Hispanic white males spent three to four fewer minutes per day in vigorous PA than Mexican American (MA; P = 0.004) and non-Hispanic black (P < 0.001) males but had lower obesity rates and obese 12- to 15-yr-old MA recorded similar minutes in MVPA per day as normal-weight MA (P > 0.050). There was a significant three-way age-body mass index-race/ethnicity interaction for mean minutes per day in MVPA (P < 0.001). Adjustment for total energy intake did not qualitatively alter these results. CONCLUSIONS Females and older youth were the least active groups. Obese youth were generally less active, but this did not hold uniformly across race/ethnic groups. Cultural or biological factors could moderate the association between PA and obesity in youth.