How breastfeeding reduces the risk of childhood obesity is unclear, and 1 hypothesis pertains to the ability of breastfed infants to self-regulate. We studied whether infants' self-regulation of milk intake is affected by feeding mode (bottle versus breast) and the type of milk in the bottle (formula versus expressed breast milk).
Participants in the 2005–2007 Infant Feeding Practices Study II received monthly questionnaires during their infant's first year, and compete data were available for 1250 infants. We tested the impact of feeding mode and type of milk during early infancy on self-regulation during late infancy.
Although only 27% of infants fed exclusively at the breast in early infancy emptied the bottle or cup in late infancy, 54% of infants who were fed both at the breast and by bottle did so, and 68% of those who were fed only by bottle did so. Multivariate regression analysis indicated that infants who were bottle-fed more intensively early in life were ∼71% or 2 times more likely to empty the bottle or cup later in life than those who were bottle-fed less intensively (⅓–⅔ or ⅔ of milk feeds given by bottle versus < ⅓ of milk feeds). When feeding formula and expressed milk were considered separately, similar dose-response relationships were observed.
Infants who are bottle-fed in early infancy are more likely to empty the bottle or cup in late infancy than those who are fed directly at the breast. Bottle-feeding, regardless of the type of milk, is distinct from feeding at the breast in its effect on infants' self-regulation of milk intake.