Determinants of the prevalence and incidence of overweight in children and adolescents.

Abstract
OBJECTIVE: To systematically analyse determinants of overweight prevalence and incidence in children and adolescents, as a basis of treatment and prevention. DESIGN: Cross-sectional and longitudinal data of the Kiel Obesity Prevention Study (KOPS). SETTING: Schools in Kiel, Germany. SUBJECTS: Cross-sectional data from 6249 students aged 5-16 years and 4-year longitudinal data from 1087 children aged 5-11 years. Weight status of students was assessed and familial factors (weight status of parents and siblings, smoking habits), social factors (socio-economic status, nationality, single parenting), birth weight as well as lifestyle variables (physical activity, media time, nutrition) were considered as independent variables in multivariate logistic regression analyses to predict the likelihood of the student being overweight. RESULTS: The cross-sectional data revealed the prevalence of overweight as 18.3 % in boys and 19.2 % in girls. In both sexes determinants of overweight prevalence were overweight and obese parents, overweight siblings, parental smoking, single parenthood and non-German nationality. High birth weight and low physical activity additionally increased the risk in boys. High media time and low parental education were significant determinants in girls. Effect of media time was mediated by maternal weight status in boys as well as by socio-economic status and age in girls. From the longitudinal data, the 4-year cumulative incidence of overweight was 10.0 % in boys and 8.2 % in girls. Parental obesity, parental smoking and low physical activity were determinants of overweight incidence in boys, whereas paternal obesity increased the risk in girls. CONCLUSIONS: Treatment and prevention should address family and social determinants with a focus on physical activity and media use.