The obesity trend in the U.S. and many other countries has increased the need for models that can assess the potential impact of alternative interventions to reverse this trend. In this paper we report on building a generic dynamic model that can be used for obesity policy analysis at multiple levels. We build an individual level model for both childhood and adulthood to capture the energy balance and weight change throughout the life of individuals, and aggregate individual level models to create population level trends of obesity. Simulated method of moments is used to estimate uncertain parameters of this model from NHANES data. The resulting model enables community, state, or national policy analysis building on a calibrated model.