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Bottle size may help explain extra weight gain in bottle-fed babies

Baby-w-bottleScientists who study childhood obesity often wonder how excess weight gain in kids can be prevented. Some experts suggest that prevention efforts should start in infancy, since formula-fed infants grow faster than those who are exclusively breast-fed.

The trouble is that no one is sure why formula feeding causes faster weight gain. Is it something about the formula itself? Are dissimilar feeding schedules responsible? Are the differences explained by the difference in demographics between families who feed with formula vs. breast milk? If we knew, perhaps pediatricians could give healthier bottle-feeding advice to moms who aren't breastfeeding.

A study published today in Pediatrics adds an interesting twist to the debate: The researchers (including Stanford's Lee Sanders, MD) found that babies fed with larger bottles between 2 and 6 months of age gained more weight.

The scientists analyzed data from 386 formula-fed babies who were part of a larger childhood obesity prevention study. (An earlier report from this study found differences in 2-month-olds' activity levels and feeding patterns that varied based on families' race and ethnicity.)

At the infants' 2-month checkup, 55 percent of parents were using bottles that held less than 6 ounces; the other 45 percent used bottles holding 6 ounces or more. There was no difference between the babies' weights or other measures of growth at 2 months, but between 2 and 6 months, the babies drinking from larger bottles had greater weight gain. After adjusting for several possible confounding factors, these infants also had higher scores on weight-for-age and weight-for-length measures.

Although bottle size is unlikely to be the only factor linking formula feeding to faster weight gain, the researchers think it's worth investigating further since it would be so easy for parents to change. Recommendations to use small bottles for babies younger than 6 months "could provide a simple intervention that is not burdensome or expensive," they write, adding:

The relationship between early parental feeding beliefs and behaviors, infant feeding behaviors, and later obesity risk should continue to be studied with valid and reliable measures in longitudinal studies. However, if a simple external influence (e.g. bottle size) can be adjusted, this method may improve concordance between an infant's nutritional needs and intake and attenuate rapid infant weight gain.

Previously: Feeding practices and activity patterns for babies vary with families' race and ethnicity, study shows, A Q&A with breastfeeding expert Susan Crowe and A little bit of formula can help with breastfeeding, new study finds
Photo by David Precious

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