Successful long-term weight-loss is exceptional, even with the best dietary and psychological interventions. Nomothetic accounts of diet failure focus on cognitive processes and emotional regulation. However, qualitative research suggests that successful dieters draw on wider understandings in explaining their success; this study extends this literature to address diet failure. Individual interviews with 10 self-selected UK dieters are analysed using IPA. Understandings of diet failure are explored and situated within wider cultural discourses. Five themes are identified: 'Dieting mode'; 'Multime'; 'Not me'; 'Modern life'; and 'Challenges of emotional and social eating'. Implications for weight-loss interventions are explored.