Associations of behavioural, psychosocial and socioeconomic factors with over- and underweight among German adolescents

Objectives: The prevalence of overweight and obesity has dramatically increased in western societies. This paper examines behavioural, psychosocial and socioeconomic factors associated with overweight and underweight among adolescents in Germany. Methods: Data from the Germanpart of the 2001/02 Health Behaviour in School-aged Children (HBSC) survey, composed of 5,650 respondents aged 11 to 17 years were analysed. Body mass index (BMI) was calculated based on self-reported weight and height. The overweight category was defined as BMI within or above the 90th percentile of specific BMI values for gender and age in the German national sample. The underweight category was defined as BMI within or below the 10th percentile of this sample. A multinomial logistic regression model was used to investigate the association between behavioural, psychosocial and socioeconomic factors and BMI categories. Results: 9.5 % of the boys and 5.4 % of the girls were classified as overweight. The prevalence of underweight was 12.6 % among boys and 19.1 % among girls. Several factors were associated with over- and/or underweight in the bivariate analysis, showing different patterns for gender and BMI categories. In the multivariable model only low family affluence, high sedentary behaviour, and being bullied (for girls only) remained positively associated with being overweight. Being underweight was negatively associated with higher age and low parental occupation; it differed also by region. Conclusion: Despite several variables being associated with overweight and underweight in bivariate models, only three factors remained associated with overweight in multivariable analysis. Other considered variables did not have independent associations with the outcome, but still could be included in respective causal pathways. Our results suggest that preventive strategies focussing on students of low socio-economic status and the avoidance of sedentary behaviours could help to address issues of overweight and obesity.