Childhood body mass index trajectories and risk of overweight and obesity in young adulthood: a population-based prospective cohort study

Childhood body mass index (BMI) change is associated with obesity in adulthood but is often investigated in isolated age windows. This study aimed to identify age windows of BMI changes that are associated with overweight, including obesity, in young adulthood. This study was embedded in a population-based, prospective cohort study among 3528 participants born in Rotterdam, the Netherlands, between 2002 and 2006. Data on gestational-age-adjusted birth weight and sex- and age-adjusted BMI (BMI-SDS) was repeatedly collected between 2 and 20 years in a dedicated research center. Associations between childhood BMI-SDS and young adult (from 17 to 21 years of age) BMI-SDS and overweight/obesity were analyzed. Of children with overweight, including obesity, at 2, 6, 10, and 14 years, 32.6%, 54.0%, 57.4%, and 70.3%, respectively, had overweight around 18 years of age. Positive deviations from the expected BMI at any age were positively associated with odds of overweight at 18, with the strongest effect estimate at 6 years (p-values < 0.05). Of children in the highest BMI tertile between 2 and 10 years, only those with BMI growth deceleration, defined as a decrease comparable to crossing a major percentile line on a growth chart, between 2 and 6 years did not have increased risk of overweight at 18 years, whereas all other children in the highest BMI tertile did. CONCLUSION: Optimizing healthy and reversing unhealthy BMI trajectories in early childhood, especially before 6 years, may be a great opportunity for the prevention of overweight and obesity. WHAT IS KNOWN: • Childhood growth and body mass index (BMI) are strongly related to obesity in adulthood. • Rapid weight gain in infancy, early childhood, and adolescence has all been found to be associated with risk of obesity in both childhood and adulthood. WHAT IS NEW: • Based on repeated growth data of 3,528 children from a prospective cohort, associations of childhood BMI with young adult BMI are strongest around age 6, compared to ages 2, 10, and 14 years old. • The increased risk of adult overweight/obesity in children in the highest BMI tertile was attenuated in those with growth deceleration before 6 years. After this age, regardless of growth velocity, risk remained increased for children in the highest BMI tertile.