Background/objectives: Early nutrition plays an important role in the development of later obesity, but it is unclear how early infant feeding impacts body mass index (BMI) trajectory. The aim of this study was to examine the influences of breastfeeding duration and timing of solid introduction on BMI z-score (BMIz) trajectory in from age 9 months to 5 years.
Methods: Data from the Melbourne InFANT Program (n=542) on breastfeeding and solid introduction, along with repeated measures of BMIz until the age of five were used for these analyses. A mixed effect polynomial model was used to investigate the effects of infant feeding type on BMIz trajectory across early childhood.
Results: With adjustment for BMI at birth and maternal characteristics including country of birth, pre-pregnancy BMI, and education level, every one month increment in breastfeeding duration was associated with 0.02 unit decrease in mean BMIz from 9 months to 5 years (P=0.004). The average mean BMIz from 9 months to 5 years of children breastfed for ≥6 months was 0.24 units lower (95%CI -0.40, -0.08 P<0.003) than those who breastfeed for less than 6 months. Breastfeeding duration ≥ 6 months demonstrated similar protective effects on BMIz among children whose mothers were healthy weight or overweight/obese pre-pregnancy. No significant association was found for timing of solid introduction and BMIz.
Conclusion: Longer breastfeeding duration was associated with lower BMIz to five years of age. Breastfeeding duration ≥ 6months showed similar beneficial effects on BMIz among children of mothers who were healthy weight or overweight/obese pre-pregnancy. The findings supports the current guidelines to prolong breastfeeding duration.