Background
Understanding the early-life development of obesity allows directing public health resources toward at-risk individuals. Distinct childhood BMI trajectories have been associated with cardiovascular risk. This study aims to refine that understanding by identifying critical periods in early life where long-term adiposity risk can be reliably predicted.
Methods
We utilised longitudinal anthropometry from the Raine Study, a population-based birth cohort (n=2,868, 1989-1991), with follow-ups spanning 1-27 years-old. Weight-for-height z-scores were calculated using both the WHO (<2 years) and the 2022 CDC BMI-for-age growth charts (2-20 years). Group-based trajectory modelling identified BMI trajectories across age intervals (1-5, 1-8, 1-13, 1-17, 1-20). Multilogistic regression assessed relative risks associated with maternal exposures and adult outcomes at age 20 and 27.
Results
Five to seven BMI trajectories were identified across all age intervals. Models from 1-5 years-old showed parallel trajectories, while those from 1-8 years and beyond revealed trajectory crossover, suggesting critical divergence before age 8. Three trajectories “very low stable”, “moderately high stable” and “very high stable”, were identifiable by age 5 and reliably tracked into adulthood. At age 8, a further two trajectories were identified, with trajectories having elevated risks of overweight/obesity at age 20 and age 27; “Very high stable” (OR = 21.4, 95% CI: 5.0-58.0), “Rising to high” (OR = 5.2, 95% CI: 2.8-9.6), “Moderately high stable” (OR 2.7, 95% CI: 1.8-4.8).
Conclusions
Models from 1-8 years captured patterns more clearly than those ending at age 5.
Our findings highlight that BMI trajectories become meaningfully distinguishable by age 8, with some risk groups identifiable even earlier. These trajectories are strongly associated with adult obesity and cardiovascular risk. Early trajectory modelling offers a powerful tool for targeted early intervention to prevent obesity.