Aim 
To examine whether breastfeeding practices are associated with body mass index (BMI) and risk of being overweight or obese (OWOB) amongst children in third grade (eight years) of elementary school.
Methods
In a regional cohort we related BMI z-scores, and presence of OWOB with breastfeeding practices including whether the child had been breastfed or not and the duration of exclusive or partial breastfeeding after adjusting for potential confounders. Parents completed questionnaires on breastfeeding and sociodemographic and lifestyle factors at school entry. Public health nurses measured height and weight. For non-participants the nurses anonymously reported these measurements together with sex and age.
Results
No significant differences were found in anthropometric measurements between participants (n=951) and non-participants (n=1,061). 90% of the children had been breastfed, and prevalence of OWOB in third grade was 21%. In adjusted analyses, BMI z-scores were not significantly related to whether or not the child had been breastfed (p=0.64), or to the duration of exclusive (mean 4.6 months, p=0.80) or partial breastfeeding (mean 10.7 months, p=0.94). Logistic regression also showed no significant association between breastfeeding measures and OWOB.
Conclusion
This study does not corroborate previous observational studies, which suggest that breastfeeding reduces the risk of childhood OWOB.

No significant associations between breastfeeding practices and overweight in eight year-old children