Reducing childhood obesity is perhaps the foremost public health priority in the U.S. and elsewhere. Our study will measure the dynamics of weight status during childhood, adolescence, and young adulthood and link these dynamics with key health outcomes during adulthood. A key contribution of our study will be to use innovative methodologies to combine 7 existing longitudinal cohorts to produce a nationally representative synthetic cohort of children and adolescents that is reflective of recent experiences. We will use recently-tested approaches to model multiple dimensions of weight dynamics, including the age and timing of obesity onset, age-specific incidence, obesity duration and intensity, weight fluctuations, and cumulative exposure to unhealthy weight (BMI-Years). We will evaluate these dynamics separately in underserved, race- ethnic minority, and rural populations of the U.S. and will estimate the role of obesity disparities in adult chronic disease.