Background: High childhood obesity prevalence has raised concerns about future adult health, generating calls for obesity screening of young children. 

Objective: To estimate how well childhood obesity predicts adult obesity and to forecast obesity-related health of future US adults. 

Design: Longitudinal statistical analyses; microsimulations combining multiple data sets. 

Data Sources: National Longitudinal Survey of Youth, Population Study of Income Dynamics, and National Health and Nutrition Evaluation Surveys.

Methods: The authors estimated test characteristics and predictive values of childhood body mass index to identify 2-, 5-, 10-, and 15 year-olds who will become obese adults. The authors constructed models relating childhood body mass index to obesity-related diseases through middle age stratified by sex and race.

Results: Twelve percent of 18-year-olds were obese. While screening at age 5 would miss 50% of those who become obese adults, screening at age 15 would miss 9%. The predictive value of obesity screening below age 10 was low even when maternal obesity was included as a predictor. Obesity at age 5 was a substantially worse predictor of health in middle age than was obesity at age 15. For example, the relative risk of developing diabetes as adults for obese white male 15-year-olds was 4.5 versus otherwise similar nonobese 15-year-olds. For obese 5-year-olds, the relative risk was 1.6. 

Limitation: Main results do not include Hispanics due to sample size. Past relationships between childhood and adult obesity and health may change in the future. 

Conclusion: Early childhood obesity assessment adds limited information to later childhood assessment. Targeted later childhood approaches or universal strategies to prevent unhealthy weight gain should be considered.