In youth, due to the changes in height and weight during the developmental period, mathematically modeling BMI is complex. Historically, this question has been addressed from one of two perspectives: (1) focused on the proper modeling but suffered from poor interpretability, and (2) focused on the applied, translational appeal but suffered from inadequate modeling. No studies to date have combined the strengths of the two perspectives in modeling children’s growth and development. Thus, this research program will aim to (1) using a large birth cohort, extend the existing models to incorporate all periods across the developmental period with a focus on the translational aspects of BMI and obesity risk, (2) cross-validate the model in another large, separate birth cohort (of which data is already obtained) and (3) compare the performance of the new model with pre-existing cross-sectional growth curves to predict BMI and adiposity changes from DXA. The current program will provide new, validated metrics to track and predict obesity risk across childhood. Study results will be used to study genetic, environmental- and behavioural-induced changes in growth across the developmental period. Given the rapid rise in childhood obesity, the applied statistical work developed here is expected to vastly improve the methodologies to characterize longitudinal growth in children.