Following the arrival of Weight Watchers UK in 1967, slimming clubs expanded rapidly in Britain in the late 1960s and early 1970s. Initially aimed at, and founded by, women, these organisations would grow into complex sites of female entrepreneurship and homosociality. Looking afresh at the relationship between women and commercialised weight loss, this article provides the first detailed study of the rise of the slimming club in mid-to-late-twentieth-century Britain. Slimming clubs were lucrative business opportunities for some women; moreover, as homosocial spaces intersecting with women’s everyday lives, they had the potential to be emotionally and psychologically empowering: a history of these organisations thus complicates feminist critiques of the slimming industry. This article draws on a variety of historical sources to piece together this forgotten history, including contemporary slimming guides, newspaper 'before-and-after' features, and oral history interviews with industry professionals and former slimming club members. Such members recognised that the commercial promise of transformation was shot through with contradictions – yet, simultaneously, slimming clubs sparked enjoyment in being in the female body and provided a space away from domesticity.