Background: Early growth rate has been linked to later obesity categorised by body mass index (BMI), but the development of body composition has rarely been studied.
Methods: We tested the hypotheses that (1) birthweight and weight gain in (2) infancy or (3) childhood are associated with later body composition, in 172 Brazilian boys followed longitudinally since birth. Growth was assessed using measurements of weight and height at birth, 6 months, and 1 and 4 y. Measurements at 9 y comprised height, weight and body composition using foot-foot impedance.
Results: Birthweight was associated with later height and lean mass (LM), but not fatness. Weight gain 0-6 months was associated with later height and LM, and with obesity prevalence according to BMI, but not with fatness. Weight gain 1-4 y was associated with later fatness and LM. Weight gain 4-9 y was strongly associated with fatness but not LM. Early growth rate did not correlate positively with subsequent growth rate.
Conclusions: Early rapid weight gain increased the risk of later obesity, but not through a direct effect on fatness. Childhood weight gain remained the dominant risk factor for later obesity. The reported link between early growth and later obesity may be due partly to hormonal programming, and partly to the contribution of LM to obesity indices based on weight and height. Whether our findings apply to other populations requires further research.