EARLY ADIPOSITY REBOUND AND THE RISK OF ADULT OBESITY

Objective. At 5 to 6 years of age, body fatness normally declines to a minimum, a point called adiposity rebound (AR), before increasing aga in into adulthood. We determined whether a younger age at AR was assoc iated with an increased risk of adult obesity and whether this risk wa s independent of fatness at AR and parent obesity. Design. A retrospec tive cohort study using lifelong height and weight measurements record ed in outpatient medical records. Setting. Group Health Cooperative of Puget Sound (GHC), a health maintenance organization based in Seattle , Washington. Participants. All 390 GHC members (and their parents) bo rn at GHC between January 1, 1965, and January 1, 1971, who had at lea st one recorded adult height and weight measurement plus two visits wi th recorded height and weight measurements in each of three age interv als: 1.5 to 4, 4 to 8, and 8 to 16 years. Main Outcome Measures. We ca lculated the mean body mass index (BMI) of each subject during young a dulthood (age 21 to 29 years) and the BMI of the parents when each sub ject was 1.5 years of age. Adult obesity was defined as a BMI greater than or equal to 27.8 for males and greater than or equal to 27.3 for females. Curves were fit to each subject's BMI values between ages 1.5 and 16 years, and the age and BMI at AR were calculated from these cu rves. Subjects were divided into tertiles of age at AR (early, middle, and late), BMI at AR, and parent BMT (heavy, medium, and lean). Resul ts. The mean age at AR was 5.5 years, and 15% of the cohort was obese in young adulthood. Adult obesity rates were higher in those with earl y versus late AR (25% vs 5%), those who were heavy versus lean at AR ( 24% vs 4%), those with heavy versus lean mothers (25% vs 5%), and thos e with heavy versus lean fathers (21% vs 5%). After adjusting for pare nt BMI and BMI at AR, the odds ratio for adult obesity associated with early versus late AR was 6.0 (95% CI, 1.3-26.6). Conclusion. An early AR is associated with an increased risk of adult obesity independent of parent obesity and the BMI at AR. Future research should examine th e biological and behavioral determinants of AR.