Dynamic Panel Modeling of Dietary Intake and Physical Activity on Weight among Chinese Men

Shu Wen Ng, University of North Carolina at Chapel Hill
Barry M. Popkin, University of North Carolina at Chapel Hill
Edward C. Norton, University of Michigan

Dynamic decisions surrounding past and present physical activities, diet and weight must be estimated jointly with correction for endogeneity and autocorrelation in these choices. Dynamic panel data models allow past realizations of the dependent variable to affect its current level and uses generalized method of moments estimators that exploit all the linear moment conditions to enlarge the set of instruments. We investigated the dynamics of weight among Chinese men and hypothesized that: a) decline in physical activity is associated with weight gain among men; b) dietary fat intake is positively related to weight; and c) physical activity is more strongly associated with weight than dietary fat intake. We used longitudinal data from men (18-55y) in the 1991-2006 China Health and Nutrition Surveys, and found that this model performs well. While the first and third hypotheses were correct, we were unable to find a significant relationship between fat intake and weight.