Infant Weight Gain: Is It the Bottle or What’s in It?

childBottle-fed infants gained more weight than breast-fed infants, even when the bottles contained pumped breast milk.

Breast-feeding is associated with less infant weight gain than formula feeding and might also lower risk for childhood obesity. One possible explanation for the more-rapid weight gain is that bottle-fed infants have difficulty regulating energy intake. Researchers examined the association between infant feeding patterns and weight gain during the first year of life in a national longitudinal study of 1899 children. Mothers (mostly white, married, and college educated) reported weight measurements at four time points and monthly percentages of feedings given by breast, breast milk from a bottle, and formula from a bottle.

Monthly weight gain was estimated using multilevel analyses and controlling for demographic factors, birth history, and infant nutritional factors (e.g., solid food introduction, sweet drinks). Estimated monthly weight gain was significantly lower in infants who were breast-fed only than in infants who were fed breast milk by bottle only (difference, 89 g), infants who were fed formula by bottle (71 g), and those fed by both breast and bottles of formula (45 g). Among infants fed breast milk only (by breast or bottle), estimated monthly weight gain increased as the percentage of breast milk feedings by bottle increased.

Comment: Although this study did not measure actual milk intake and was limited to predominantly white and college-educated mothers, the results support the authors’ hypothesis that bottle feeding, regardless of the type of milk in the bottle, is associated with increased weight gain. The association makes sense because breast-fed infants largely decide when a feeding is over, whereas bottle-fed infants are often encouraged to finish the bottle, especially if it contains valuable pumped breast milk. Should mothers avoid bottle feeding? Editorialists rightly note that infants are fed pumped breast milk and formula from a bottle for many practical reasons, and although breast-feeding is ideal, parents need not feel guilty if it is not always possible. Cornelius W. Van Niel, MD

Published in Journal Watch Pediatrics and Adolescent Medicine June 20, 2012

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