Physical Activity, Body Mass Index, and Media Use Among School-Age Children

Purpose. Regular physical activity (PA) in childhood is a predictor of regular PA in adulthood. Few studies have assessed PA using metabolic equivalents per minute (met-mins; Ainsworth, 2000) in a large population of US youth. The study's purpose is to investigate the relationship between PA, measured using the National Health and Nutrition Examination Survey (NHANES) PA and Physical Fitness Questionnaire, which were then converted into met-mins, BMI classification and media use among US school-age children. Methods. A sample of children and adolescents (n=1501) from grades K-12 was selected from the 2005-2006 NHANES. Daily met-mins were summed for each participant to get a total met-mins of activity per week for each individual. Analysis/Results. Descriptive statistics were computed using SAS and SUDAAN. Linear regression analysis was used to detect significant relationships between met-mins and several independent variables including grade level, BMI classification, computer use, and TV use. Grade Level. High School students had significantly higher met-mins than elementary and middle school students (p<0.001) and boys had significantly higher met-mins than girls (p<.001). BMI Classification. Average met-mins for children who were underweight, normal weight, overweight, and obese were 1131, 1364, 1125, and 1080, respectively. Youth who were underweight, overweight, and obese obtained significantly less PA, measured as met-mins, than youth categorized as having a normal BMI-for-age (p=0.03). Media Use. The variable met-mins was significantly and inversely associated with television viewing time (p=0.02). Youth who watched more than five hours of television had 272 fewer met-mins than those who watched no television at all. Time spent on a computer was not related to number of met-mins. Conclusions. BMI classification, hours of TV, education level, and gender were significantly related to PA, measured in met-mins, while hours of computer use was not related. Programs are needed that allow “all” children, specifically girls, overweight and obese youth, and elementary students, to participate in PA. We should continue to advocate for policies requiring PE throughout the K-12 years and should also support before and after school PA programming for youth.