How ‘responsibility’ for healthy eating is perceived and allocated has implications for the way people act, with consequences for population health. Although ‘responsibility’ features in health policy and corporate strategy, its meaning is equivocal. The aim of this research is to determine how selected, key actors in the food system discursively construct responsibility for diet and concomitant population health, and what supports or constrains their ability to be ‘responsible’. This project uses a qualitative approach, contextualised in a complex systems framework. Three types of data were gathered: existing corporate and government publications, focus groups with members of the public and semi-structured interviews with representatives from government, industry and NGOs. Foucauldian discourse analysis was carried out on the dataset to explore the discourse of responsibility in the food system and the power dynamics that underpin it. Analysis showed that perceptions of responsibility mediate behaviours within the food system and that the seemingly common sense discourse of individual responsibility for healthy eating is undermined by others such as those of choice and complexity. Yet the discourse of choice belies the degree to which individuals are constrained in making rational, truly ‘free’ choices in the food system. Indeed, power over, and therefore responsibility for the main determinants of food choice e.g. taste, cost, convenience and promotions, were seen to lie with government and industry. The findings suggest that discourses of responsibility mask the commercial determinants of food choice, sanctioned by government, underpinned by neoliberal commitments to the free market and individualism. Overall, the data showed that responsibility for healthy eating is not proportional to the power different actors have over determinants of dietary choice. The concept of ‘proportional responsibility’ is proposed as a potential framework for apportioning fair responsibility between actors in the food system.