Although necessary for a normal final height in individuals who were born small for gestational age (SGA), catch-up growth is associated with drastic changes in body composition that have been suspected to favor the later development of the long-term metabolic complications by promoting central adiposity; however, the specific contribution of catch-up itself on these later complications remains unclear. Therefore, the aim of the study was to characterize the dynamic changes in adiposity during childhood in individuals who were born SGA and to investigate their consequences on adulthood. The magnitude and the time course of postnatal changes in body mass index (BMI) relative to birth and their consequences on adult adiposity were investigated in 127 adults who were born SGA and had available serial anthropometric data in childhood (0-6 y) and adulthood. Catch-up in BMI, observed in 91% of individuals who were born SGA, was mostly completed within the first or second year of age. Overall, adult BMI was correlated with the magnitude of gain in BMI during childhood. However, this effect was significant only when this gain persisted after the first year of life. Similarly, the influence of the magnitude in gain in BMI on the risk for adult BMI >25 kg/m(2) was significantly influenced by the age at which the gain in BMI occurred. In summary, although the extent of catch-up in BMI affects adiposity in adulthood, this effect is mostly deleterious when occurring after 1 y of age, suggesting that a rapid catch-up process should be more suitable than a delayed one. Whether this observation holds through regarding the metabolic syndrome remains to be elucidated.