The aim of this project is to provide a comprehensive investigation of the relationship between food prices and food advertising on childhood obesity using multiple data sources that span the period of the last three decades, as well as using the latest advances in technology for measuring obesity and physical fitness among children. More specifically, this work involves: (a) developing a method for imputing children’s body composition to serve as an alternative to BMI-based obesity measures and to make these measures available for social scientists who study childhood obesity using social science datasets, (b) using body composition measures to conduct a comprehensive analysis of the effects of food prices, food outlets, and fast-food restaurant advertising on television on obesity among children ages 8-18; (c) examining whether the effects of food prices and food advertising on obesity differ between adolescents from low socio-economic backgrounds and other adolescents; and (d) testing the sensitivity of these findings against previous research using BMI.