This paper presents a critical discourse analysis of the UK government's 'Change4Life' antiobesity social marketing campaign, which uses colourful cartoon characters and simplified messages to 'reframe' the issue of obesity, and encourage the public to take an active role in addressing this policy problem. It stems from a wider political context in which insights from behavioural economics ('nudge') are increasingly turned to for solutions to policy problems. The approach particularly emphasises the importance of carefully crafted communication in securing public compliance with desired policy outcomes, and has gained considerable attention in political science, economics, and health research. This paper contributes to that growing debate by offering a systematic textually-oriented critical analysis of the discourse of nudge. It maps the public, private, and third sector practices comprising this campaign, and critically examines the underlying balance of power and vested interests. Detailed analysis of the launch advert and surrounding policy documents reveals how scientific claims about obesity are recontextualised, simplified, and distorted in this campaign. It is further argued that the use of behavioural psychology legitimate individualised policy solutions, squeezing out public deliberation over the complex structural causes of obesity.