ABSTRACT
This chapter discusses the causality in epidemiology, drawing out the implications that established theoretical and methodological positions have for research on obesity. The notion of direction in causality suggests the existence of a causal pathway between cause and effect. Research in social epidemiology generally considers causality in relation to criteria set out by Austin Bradford Hill. The absence of randomization in observational epidemiology and, to a lesser extent, the issue of directionality are problematic because of their implications for confounding. The ecological study of Drewnowski linked the prevalence of overweight children with neighbourhood poverty and suggested that ethnicity was not a mediating factor. A study of a child and adolescent population in Canada reveals that children in areas with good access to activity provision parks, playgrounds are less likely to be obese. Interaction and synergy between possible causal variables are important concepts that can render weak individual relationships stronger when placed alongside others.
