OBJECTIVE: To examine the association between breastfeeding and obesity in school-age children from Brazilian families of high socioeconomic status. METHODS: A cross-sectional study was conducted including 555 students aged six to 14 years from a private school in the city of Sao Paulo. Obesity - the outcome variable - was defined as body mass index at or above the 85th centile plus sub scapular and triceps skin folds at or above the 90th centile using the sex and age specific standards of the US National Center for Health Statistics. Exposure was the frequency and duration of breastfeeding. Potential confounders, controlled for using multiple logistic regression, included child sex, age, birthweight, and dietary and physical activity patterns, and maternal age, body mass index, schooling, and practice of sports or physical exercise. RESULTS: Prevalence of obesity in the studied population was 26%. After confounder adjustment, the risk of obesity in children that had never been breastfed was twice that of other children (OR=2.06; 95% CI: 1.02; 4.16). There was no dose-response effect of duration of breastfeeding on prevalence of child obesity. CONCLUSIONS: Children who were never breastfed showed greater prevalence of obesity at school age. The absence of a dose-response effect in the relationship between duration of breastfeeding and prevalence of obesity and the still controversial findings regarding this association reported by other authors indicate a need for further studies on the subject, in particular studies with longitudinal design.
Obesity; Child; Adolescent; Breast feeding; Social class; Body mass index; Cross-Sectional Studies
