OBJECTIVE To examine whether maximal velocities of weight, height and fat mass during potentially critical periods of growth were associated with body composition in young adulthood. METHODS Analyses were performed on 277 female and 271 male participants of the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study with anthropometric measurements in young adulthood (18-25 years) as well as early life (0-2 years), mid-childhood (3-8 years) or puberty (9-15 years). Maximum growth velocities were calculated using the SuperImposition by Translation And Rotation (SITAR) routine or polynomial functions and related to adult fat mass index (FMI) and fat-free mass index (FFMI). RESULTS In early life, faster weight gain was associated with a moderately higher FMI and FFMI in young adulthood in women only (Ptrend=0.01). In mid-childhood and puberty, weight and fat mass velocities were related to adult FMI and FFMI in both sexes (Ptrend⩽0.002): relative differences between the highest and lowest tertiles of these growth velocities ranged 33-69% for adult FMI and 6-12% for adult FFMI. A higher mid-childhood height velocity was related to a modestly higher adult FMI in women only (Ptrend=0.0005). CONCLUSIONS Faster gain in weight and body fat during mid-childhood and puberty appear to be particularly relevant for adult fat mass.