Is breastfeeding protective against child obesity?

Recent studies suggest that breastfeeding reduces the risk of child obesity to a moderate extent. Of 11 studies that examined prevalence of overweight in children older than 3 years of age and that had a sample size of > or = 100 per feeding group, 8 showed a lower risk of overweight in children who had been breastfed, after controlling for potential confounders. The 3 "negative" studies lacked information on the exclusivity of breastfeeding. A dose-response relationship with duration of breastfeeding was observed in some, but not all, of the "positive" studies. Possible mechanisms include learned self-regulation of energy intake, metabolic programming in early life, and residual confounding by parental attributes. If the association is causal, the effect of breastfeeding is probably small compared to other factors that influence child obesity, such as parental overweight. Nonetheless, it may be of public health significance considering the current epidemic of child overweight.