Rapid growth among term children whose birth weight was appropriate for gestational age has a longer lasting effect on body fat percentage than on body mass index

Background: It is not clear whether and how rapid growth in infancy, a risk factor for later obesity, differentially affects growth and body-composition development throughout childhood in term children with an appropriate-for-gestational age (AGA) birth weight. Objective: The aim was to examine the effect of rapid growth in infancy on body mass index SD score (BMI SDS) and body fat percentage (%BF) trajectories until age 7 y. Design: This analysis included 206 (50.5% female) AGA term participants of the Dortmund Nutritional and Anthropometric Longitudinally Designed Study. Repeated anthropometric measurements were obtained between 0.5 and 7 y of age. Results: Fifty-nine of the 206 children (28.6%) displayed rapid growth (an increase in SDS for weight of > 0.67 between birth and age 2 y). From 6 mo of age, their growth trajectories diverged from normal growers, and by age 7 y they had a higher BMI, more fat mass, and a higher risk of overweight (odds ratio: 6.2; 95% CI: 2.4, 16.5; P = 0.0002). Multilevel model analyses showed that the differences in BMI were achieved within the first 2 y of life [beta (+/- SE) SDS: 1.22 +/- 0.13], after which they persisted at this level until the age of 7 y, whereas differences in %BF, which were also already discernible by age 2 y (1.52 +/- 0.34%), became progressively larger over the next 5 y (adjusted difference: 0.23 +/- 0.11%/y; P = 0.03). Conclusions: Rapid growth in infancy and early childhood results in an increased BMI and %BF throughout childhood and an increased risk of overweight at age 7 y among AGA children. Rapid growth in AGA children has a more pronounced effect on %BF than on BMI.