Abstract
OBJECTIVE: To evaluate the association between duration of breastfeeding (BF) and obesity in schoolchildren of Florianópolis (SC), and the role of possible effect modifiers. METHODS: Cross-sectional study with a random sample of 2826 schoolchildren (7-14 years). Weight and height were measured according to standardized procedures. Data concerning BF and sociodemographic variables were obtained from a questionnaire sent to parents/guardians. Children's nutritional status was evaluated by BMI-for-age z-score for gender (WHO reference curves). Adjusted analyses were performed through logistic regression, considering a possible interaction among variables. RESULTS: Prevalence of obesity was 8.6% (95% CI: 7.6-9.7%) and 55.7% (95% CI: 53.8-57.6%) received breastmilk for ≥6 months. BF was not associated with obesity, even in the adjusted analysis. Stratified analysis according to maternal schooling showed that, in children aged 7-10 years and children whose mothers had 0-8 years of schooling, the chance of obesity was lower among those breastfeed for >1 month, especially among those who received breastmilk for 1-5 months (OR=0.22; 95% CI 0.08-0.62). Among children of women with higher schooling (>8 years), the chance of obesity was 44% lower in those who were breastfed for >12 months (p-value for interaction <0.01). This interaction was not found in older children (11-14 years). CONCLUSIONS: Among children of women with lower schooling, BF for any period longer than 1 month is protective against obesity; however, for a higher maternal schooling, BF for less than 12 months increases the odds of obesity.