Parental overweight, socioeconomic status and high birth weight are the major determinants of overweight and obesity in 5-7 y-old children: baseline data of the Kiel Obesity Prevention Study (KOPS).

OBJECTIVES: To identify the major risk factors of overweight and obesity in prepubertal children.
DESIGN: Cross-sectional study.
SETTING: In all, 32 primary schools in Kiel (248 000 inhabitants), northwest Germany.
SUBJECTS: A total of 2631 5-7-y-old German children and their parents. MAIN OUTCOME MEASURES: Weight status, socio-economic status (SES), parental overweight, dietary intake, activity, inactivity and further determinants (birth weight, breast feeding, nutritional status of siblings) of the children.
RESULTS: The prevalence of overweight (>/=90th BMI percentile of reference) was 9.2% in boys and 11.2% in girls, respectively. Considered univariately, family-, environment- and development-related determinants showed some relations to overweight and obesity. In multivariate analyses parental overweight, a low SES as well as a high birth weight were the strongest independent risk factors of overweight and obesity in children. Additionally, there were sex-specific risk factors: parental smoking and single households were risk factors in boys, whereas a low activity was associated with obesity in girls. Birth weight was associated with obesity, but not with overweight. The prevalence of obesity reached 29.2% in boys and 33.4% in girls with all the three main risk factors.
CONCLUSIONS: Overweight families of low SES have the highest risk of overweight and obese children. Future prevention programmes must also take into account sex-specific risk factors.