Drawing on evidence from the Framingham Heart Study, Christakis and Fowler in their 2007 article published in the New England Journal of Medicine make the claim that obesity spreads in social networks. Whether they are correct in this assertion is neither the concern nor focus of this article. Rather, what is of interest is the subsequent mobilisation of ‘contagion’ to describe this spread and to account for the emergence of an ‘obesity epidemic’ in contemporary society. Contrary to the argument that there is less stigma attached to obesity, the reporting of the Christakis and Fowler article suggests that being ‘fat’ remains a signifier of moral and physical decay; if we add to this the suggestion that obesity is spread within social networks, it is possible that the stigma associated with body size will begin to mirror that which is attached to other infectious bodies. In order to consider the potential implications of this, the article develops in three directions: it explores the application of contagion as a metaphor for understanding the spread of obesity; it sets this understanding within the context of scholarship on contagion and it draws on critical obesity studies literature to call for a more cautionary approach to be taken when deploying a term that when combined with pre-emptive public health discourse would add significantly to the pathologising of the corpulent, fat or obese body.