Abstract P085: Infant Weight and Length Trajectories Have Different Impacts on Body Composition at Age 3

Abstract

Introduction: Rapid infant weight gain has been linked with higher childhood body mass index (BMI) and risk of obesity. However, because BMI cannot distinguish lean from fat mass, the role of infant weight or length trajectories on childhood body composition is unclear. Hypothesis: This study aimed to evaluate how specific aspects of infant growth trajectories are associated with fat mass, lean mass and % body fat at age 3. Methods: Total 323 children age 3 y (46% female, 20% African-American) had body composition measured by dual-energy x-ray absorptiometry, and weight and length measurements from birth to age 2 y from pediatrician growth charts. Growth trajectories were characterized using the SuperImposition by Translation And Rotation (SITAR) model. This technique estimates an average growth curve with random effects that allow individual growth curves to shift up or down (size), shift right or left on the age axis (tempo) or rotate to steepen/flatten the growth curve (velocity). Tempo did not improve model fit so was excluded. Size and velocity parameters for weight and length trajectories were regressed against fat mass (FM), lean mass (LM) and % body fat measurements at age 3. Results: On average, girls had higher FM (3.9 vs. 3.4 kg) and lower LM (8.8 vs. 9.5 kg) than boys. Adjusting for sex, LM at age 3 was significantly higher with greater weight velocity and with longer length size between ages 0-2 (Table), but were not related to length velocity or weight size. Adjusting for sex, higher FM was seen for those with higher weight size between ages 0-2, but was not related to either weight or length velocities. Percent body fat at age 3 was associated with both larger weight size and shorter length size between 0-2 years of age, but not with either growth velocities. Conclusions: Weight and length size and velocity differ in their impact on children’s body composition by age 3. This study suggests that faster early weight gain (higher weight velocity) and longer lengths but not higher overall weight may lead to leaner body composition by age 3.