Formula-fed infants may be at greater risk for overfeeding and rapid weight gain. Different size bottles are used for feeding infants, although little is known about whether bottle size is related to weight gain in bottle-fed infants.
Data from the Greenlight Intervention Study, a cluster randomized trial to prevent childhood obesity at 4 pediatric resident clinics, were used to analyze the exposure to regular (<6 oz) or large (≥6 oz) bottle size at the 2-month visit on changes in weight, weight-for-age z score (WAZ), and weight-for-length z score (WLZ) at the 6-month visit. Using multivariable regression, we adjusted for potential confounders (birth weight, gender, age, weight measures at 2 months, parent race/ethnicity, education, household income and size, time between 2- and 6-month visits, and first child status).
Forty-five percent (n = 386; 41% black, 35% Hispanic, 23% white, 2% other) of infants at the 2-month visit were exclusively formula-fed, and 44% used large (≥6 oz) bottles. Infants whose parents fed with large bottles had 0.21 kg (95% confidence interval [CI]: 0.05 to 0.37) more weight change, 0.24 U (95% CI: 0.07 to 0.41) more change in WAZ, and 0.31 U (95% CI: 0.08 to 0.54) more change in WLZ during this period than infants fed with regular bottles.
Using a large bottle in early infancy independently contributed to greater weight gain and change in WLZ at the 6-month visit. Although growth in infancy is complex, bottle size may be a modifiable risk factor for rapid infant weight gain and later obesity among exclusively formula-fed infants.