Systematic Examination of Infant Size and Growth Metrics as Risk Factors for Overweight in Young Adulthood

OBJECTIVE To systematically examine infant size and growth, according to the 2006 WHO infant growth standards, as risk factors for overweight status in young adulthood in a historical cohort. Specifically, to assess: Whether accounting for length (weight-for-length) provides a different picture of risk than weight-for-age, intervals of rapid growth in both weight-for-age and weight-for-length metrics, and what particular target ages for infant size and intervals of rapid growth associate most strongly with overweight as a young adult. PATIENTS/METHODS Data analysis of 422 appropriate for gestational age white singleton infants enrolled in the Fels Longitudinal Study. Odds ratios (OR) for overweight and obesity in young adulthood (age 20-29) were calculated using logistic regression models for the metrics at each target age (0, 1, 3, 6, 9, 12, 18, 24 months) comparing ≥85(th) v. <85(th) percentile, as well as rapid growth (Δ≥0.67 Z-score) through target age intervals. Models accounted for both maternal and paternal BMI. RESULTS Infants ≥85(th) percentile of weight-for-age at each target age (except 3 months) had a greater odds of being overweight as a young adult. After accounting for length (weight-for-length) this association was limited to 12, and 18 months. Rapid weight-for-age growth was infrequently associated with overweight as a young adult. Rapid weight-for-length growth from 0 to 24 months, 1 to 6, 9, 12, 18, and 24 months and from 3 to 9, 12, 18, and 24 months was strongly associated with overweight status as a young adult. CONCLUSIONS The WHO weight-for-length metric associates differently with risk of being overweight as a young adult compared to weight-for-age. Intervals of rapid weight-for-length growth ranging from months (0-24), (1-12, 18, and 24) and (3-9, and 12) displayed the largest OR for being overweight as a young adult.