BACKGROUND & AIMS: : To determine if rapid growth between 0 and 2 years of life influences body composition and resting energy expenditure (REE) measured at 12-14 years in a population of obese children. METHODS: REE and body composition were measured in 107 obese children aged 12-14 years in whom weight at birth and 2 years was recorded. RESULTS: 46 obese children had a rapid growth between birth and 2 years (>0.67 SD). Rapid weight gain was positively correlated with weight and height at 12-14 years but not with body mass index (BMI). Fat mass (FM) to fat free mass (FFM) ratio was not significantly different at 12-14 years in children with rapid or normal growth velocity. REE in 12-14 year-old children with rapid growth (1765±222kcal/24h) was significantly higher than children with normal growth velocity (1586±216kcal/24h) (P<0.001). REE adjusted for FFM was similar in the two groups. CONCLUSIONS: Rapid weight gain between 0 and 2 years of life is associated with higher weight, height, FFM, FM and REE in 12-14 year-old obese children despite identical BMI. These data demonstrate that growth velocity affects later body composition and REE in obese adolescents but relationship between REE and FFM is preserved.