Theoretical models suggest that decisions about diet, weight and health status are endogenous within a utility maximisation framework. In this paper, we model these behavioural relationships in a fixed-effect panel setting using a simultaneous equation system, with a view to determining whether economic variables can explain the trends in calorie consumption, obesity and health in OECD countries and the large differences among countries. The empirical model shows that progress in medical treatment and health expenditure mitigates mortality from diet-related diseases, despite rising obesity rates. While the model accounts for endogeneity and serial correlation, results are affected by data limitations.