Greater within-person weight variability during infancy predicts future increases in z-BMI

This study tested the hypothesis that greater weight variability (WV; measured as root mean square error [RMSE]) during the first year of life predicts weight gain at year two and greater WV during the second year of life predicts greater weight gain at year three.

This was a prospective study using mother and offspring data from the Avon Longitudinal Study of Parents and Children. Infant z-BMI (BMI z score) and WV scores were calculated separately during years one and two. Maternal demographic, weight, and nursing-related measures were also used in analyses.

Sample sizes in year-one and year-two analyses were 814 (448 male; 366 female) and 783 (432 male; 351 female), respectively. RMSE in year one significantly predicted z-BMI change in year two (β [SE]: 0.32 [0.12]; p = 0.01; adjusted R² = 0.07), controlling for z-BMI change in year one and z-BMI at birth. Similar significant prediction was found using year-two RMSE for year-three z-BMI (β [SE]: 0.33 [0.14]; p = 0.02; adjusted R² = 0.10). Maternal characteristics were not related to RMSE in year one or year two.

Previous findings that WV predicts subsequent increases in body mass in adults were, for the first time, extended to infants.