The Relation of Adiposity Rebound to Subsequent BMI in a Large Electronic Health Record Database

Objective: The beginning of postinfancy increase in BMI has been termed the adiposity rebound, and an early rebound increases the risk for obesity in adolescence and adulthood. We examined whether the relation of the age at BMI rebound (agerebound) to subsequent BMI is independent of childhood BMI. Design: From the electronic health records of 2.8 million children, we selected 17,077 children examined at least once each year between ages 2 and <8 years, and who were reexamined between age 10 and <16 years. The mean age at the last visit was 12 years (SD = 1). We identified agerebound for each child using lowess, a smoothing technique. Results: Children who had an agerebound <3 years were, on average, 6.8 kg/m2 heavier after age 10 years than were children with an agerebound >7 years. However, BMI after age 10 years was more strongly associated with BMI at the rebound (BMIrebound) than with agerebound (r = 0.63 vs.-0.49). Although the relation of agerebound to BMI at the last visit was mostly independent of the BMIrebound, adjustment for age-5 BMI reduced the association's magnitude by about 55%. Conclusions: Both agerebound and the BMIrebound are independently related to BMI and obesity after age 10 years. However, a child's BMIrebound and at ages 5 and 7 years accounts for more of the variability in BMI levels after age 10 years than does agerebound.