Background: There is a paucity of empirical data assessing the effect of obesity prevention policies across the socioeconomic gradient of population weight. We therefore aimed to develop a theoretical framework that will enable organisation of current and future universal obesity prevention interventions into their likely impact on the socioeconomic gradient of population weight gain.

Methods: We partitioned the framework into two scales; the environment where action is taken (micro and macro environments) and the degree to which an intervention targets individual agency or embedded structures to influence behaviour change (characterised by three predominant policy types: agentic, agento-structural and structural).

Results: Agentic interventions, which are heavily reliant on individual agency, are more likely to increase socioeconomic inequalities in population weight. Examples of these types of interventions include social marketing, school nutrition education programs and signage to encourage healthy behaviours. Structural interventions generally describe an equal or greater benefit for lower socioeconomic groups and include food procurement policies, restricting the availability of unhealthy foods in schools and a mandatory increase in school physical education time. Agento-structural interventions are mindful of the environment in which health behaviours take place, but individual agency is nonetheless important. Agento-structural interventions include work place design to encourage incidental exercise and mandatory nutrition labelling. There is a lack of empirical evidence and theoretical clarity regarding the socioeconomic impact of agento-structural interventions, however we hypothesise that those aimed at the macroenvironmental context are more likely to have an equitable impact.

Conclusions: Examination of the socioeconomic health impact of obesity prevention interventions is crucial. This is especially true for agento-structural interventions, which show great promise for obesity prevention, but where the greatest uncertainty regarding the socioeconomic health impact remains. Failure to do so runs the risk of widening the socioeconomic gradient in health as we strive to prevent obesity.