Associations of infant feeding and timing of linear growth and relative weight gain during early life with childhood body composition.

BACKGROUND: Growth and feeding during infancy have been associated with later life body mass index. However, the associations of infant feeding, linear growth and weight gain relative to linear growth with separate components of body composition remain unclear. METHODS: Of 5551 children with collected growth and infant-feeding data in a prospective cohort study (Amsterdam Born Children and their Development), body composition measured using bioelectrical impedance analysis at the age of 5-6 years was available for 2227 children. We assessed how feeding (duration of full breastfeeding and timing of introduction of complementary feeding) and conditional variables representing linear growth and relative weight gain were associated with childhood fat-free mass (FFM) and fat mass (FM). RESULTS: Birth weight was positively associated with both FFM and FM in childhood, and more strongly with FFM than FM. Faster linear growth and faster relative weight gain at all ages in infancy were positively associated with childhood FFM and FM. The associations with FM were stronger for relative weight gain than for linear growth (FM z score: ß coefficient 0.23 (95% con 0.19 to 0.26), P<0.001 and 0.14 (0.11 to 0.17), P<0.001 per s.d. change in relative weight gain and linear growth between 1 and 3 months, respectively). Compared with full breastfeeding <1 month, full breastfeeding >6 months was associated with lower FM (FM z score: -0.17 (-0.28 to -0.05), P=0.005) and lower FFM (FFM z score: -0.13 (-0.23 to -0.03), P=0.015), as was the introduction of complementary feeding >6 months (FM z score: -0.22 (-0.38 to -0.07), P=0.004), compared with <4 months. CONCLUSIONS: Faster infant weight gain is associated with a healthier childhood body composition when it is caused by faster linear growth. Full breastfeeding >6 months and introduction of complementary feeding >6 months are associated with lower childhood FM.