Early Growth and Body Composition in Infancy

Examination of the relationship between early growth and body composition (BC) in infancy might provide clues about the mechanism of early nutrition programming. 150 healthy full-term infants (64 boys) born in Cambridge from 1985–1993 had BC measured using stable isotope at the age of 12 weeks as a part of infant nutrition studies. Fat mass index (FMI, FM/length²) and lean mass index (LMI, LM/length²) internal standard deviation scores (SDS) were calculated for boys and girls. Birth weight SDS was positively associated with length, BMI and FMI SDS at 12 weeks, but not LMI SDS; equivalent to 0.26 SDS increase in FMI per 1 SDS increase in birth weight (95% CI, 0.04–0.48). Weight SDS change from birth-12 weeks was positively correlated with FMI and LMI SDS at 12 weeks; equivalent to 0.68 SDS and 0.48 SDS increase in FMI and LMI per 1 SDS gain in weight (95% CI, 0.48–0.88 and 0.26–0.70, respectively). Associations were independent of gender, parity, infant diets, and, for weight gain, birth weight SDS. Conclusion: Higher birth weight was associated with higher fat mass at 3 months whereas rapid weight gain in the first 3 months was associated with both fat and lean mass. Our data do not support the hypothesis that lean mass tracks directly from fetal life to childhood.