Prevalence of and risk factors for childhood overweight and obesity.

Background: Increases in childhood overweight and obesity have become an important public health problem in industrialized nations. Preventive public health action is required, but more research of risk factors is required before evidence-based initiatives can be developed and targeted effectively. We investigated the association between childhood overweight and obesity and risk factors relating to dietary habits, activities, parents and schools.

Methods: In 2003 we surveyed grade 5 students and their parents and school principals in Nova Scotia. We measured height and weight and assessed dietary habits (using Harvard's Youth/Adolescent Food Frequency Questionnaire), physical and sedentary activities, and parental and school-based risk factors. We estimated neighbourhood income by averaging, per school, the postal-code level means of household income of residential addresses of children attending that school. We used multilevel logistic regression to evaluate the significance of these risk factors for overweight and obesity.

Results: On the basis of measurements taken of 4298 grade 5 students, we estimated the provincial prevalence of overweight to be 32.9% and of obesity to be 9.9%. Children who bought lunch at school were at increased risk of overweight (fully adjusted odds ratio [OR] 1.39, 95% confidence interval [CI] 1.16-1.67), whereas those who ate supper together with their family 3 or more times a week were at decreased risk (OR 0.68, 95% CI 0.52-0.88). Physical education classes 2 or more times a week at school were associated with a decreased risk of overweight (OR 0.61, 95% CI 0.43-0.87) and obesity (OR 0.54, 95% CI 0.33-0.88). Children in high-income neighbourhoods were half as likely to be obese as their peers living in low-income neighbourhoods (OR 0.50, 95% CI 0.36-0.70).

Interpretation: Parents and schools provide important opportunities for public health initiatives for reducing childhood overweight and obesity. Children and schools in low-income neighbourhoods should receive priority in public health initiatives to reduce future socioeconomic inequalities in health.