Formula-fed infants gain weight more rapidly, out of proportion to linear growth
Weight gain is quicker and out of proportion to linear growth among formula-fed infants compared with predominantly breastfed ones, a recent study has found.
To investigate the associations of infant feeding with trajectories of growth and body composition from birth to 7 months in healthy infants, researchers analysed 276 participants from a previous study of maternal vitamin D supplementation during lactation. Mothers used monthly feeding diaries to report the extent of breastfeeding.
Researchers measured infants’ anthropometrics and used dual-energy X-ray absorptiometry to evaluate body composition at 1, 4 and 7 months. Changes in infant size (z scores for weight, length and body mass index [BMI]) and body composition (fat and lean mas, body fat percentage) were compared between predominantly breastfed and formula-fed infants, adjusting in linear regression for sex, gestational age, race/ethnicity, maternal BMI, study site and socioeconomic status.
Of the participants, 214 (78 percent) were breastfed (median duration 7 months) and 62 were exclusively formula fed.
Formula-fed, compared with breastfed, infants had lower birth-weight z scores (‒0.22 vs 0.16; p<0.01) but gained more in weight and BMI through 7 months of age (weight z score difference, 0.37; 95 percent CI, 0.04 to 0.71; BMI z score difference, 0.35; 0 to 0.69). There was no difference seen in linear growth (z score difference, 0.05; ‒0.24 to 0.34).
Compared with breastfed infants, formula-fed ones gained more lean mass (difference, 303 g; 137 to 469 g) but not fat mass (difference, ‒42 g; ‒299 to 215 g).
“These differences were attributable to greater accretion of lean mass, rather than fat mass,” researchers said. “Any later obesity risk associated with infant feeding does not appear to be explained by differential adiposity gains in infancy.”