The focus on body size or weight has become an increasing source of concern in western society, yet few studies have looked at how people invoke body size in various settings, and the practices to which such talk might be related. Hence this study examines instances in everyday and institutional interaction in which body size is treated as a relevant concern for speakers. A discursive psychological approach is used to examine five extracts from telephone calls to a National Society for the Prevention of Cruelty to Children (NSPCC) helpline. The analysis focuses on how the weight or body size of others is constructed and managed, and how these descriptions can be involved in various activities. Three analytic themes emerge – the focus on how formulations of size and embodiment are drawn upon in practice; the relationship between issues of size and issues of knowledge; and the activities in which different size descriptions are enrolled, in particular, the way these activities relate to the institutional practices of the NSPCC helpline. The empirical claims about the data are also related back to basic theoretical questions, raising profound issues about the way traditional psychology has constructed eating and embodiment.