title: Lack of association between television viewing, soft drinks, physical activity and body mass index in children.
abstract: OBJECTIVE
  To examine the cross-sectional and longitudinal associations of physical activity, screen time and dietary habits on the body mass index (BMI) of children.
  
  
  METHODS
  A cohort of 122 girls and 146 boys (age at entry 10 years) from three rural states in the western USA was studied over an 18-month period. Subjects were measured for height and weight. Habitual physical activity, screen time (television viewing, video games and computer use) and dietary variables were assessed by a questionnaire. Cross-sectional and longitudinal analyses were conducted to examine the associations between physical activity, screen time and diet with BMI at baseline and follow-up and change in BMI.
  
  
  RESULTS
  At baseline, approximately 10% of boys and girls were obese and 17.8% of boys and 14.8% of girls were overweight. BMI showed a high degree of stability for boys and girls (r = 0.90), whereas physical activity, screen time and dietary habits showed moderate stability (r = 0.31-0.50) across the 18-month period. Cross-sectional and longitudinal correlations between physical activity, screen time, diet and BMI were low and non-significant (r < 0.15). The regression models explained between 8% and 22% of the variance in the change in BMI; however, none of the predictor variables were statistically significant.
  
  
  CONCLUSIONS
  Physical activity, screen time and dietary habits were not significantly related to the BMI in cross-sectional or longitudinal analyses. Further research is warranted to better understand the complex, multifactorial phenotype of the BMI in growing and maturing children.
authors.affiliation: Department of Kinesiology Ames, IA, USA. jce@msu.edu
authors.forename: Kelly
authors.initials: K
authors.lastname: Laurson
authors.forename: Joey C
authors.initials: JC
authors.lastname: Eisenmann
authors.forename: Sylvia
authors.initials: S
authors.lastname: Moore
mesh_terms: D015992:Body Mass Index; D002253:Carbonated Beverages; D002648:Child; D003430:Cross-Sectional Studies; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009043:Motor Activity; D009752:Nutritional Status; D009765:Obesity / Q000209:etiology; D050177:Overweight / Q000209:etiology; D012307:Risk Factors; D012424:Rural Population; D011795:Surveys and Questionnaires; D013690:Television; D013997:Time Factors