This paper asks how identity-making across the life course might best be theorised. Whilst the limitations of both foundationalist and anti-foundationalist accounts of the body are now established, the body nonetheless remains central to such a theoretical project. Using a case study of debates surrounding sexual and reproductive health, we offer an approach which roots itself in human embodiment. Whilst medical science has pushed back the material limits of bodily ageing in ways which promise delivery of the "postmodern life course", modernist legacies of a naturalised chronology of ageing persist. Evident within media debates is a regulatory framework which uses a naturalist discourse to contest the transgression of age-based sexual and reproductive identities. What this paper argues for is an approach to the body which shows how regulatory structures of this kind both impinge upon its materiality, but are also resisted through the embodied agency of individuals.