Previous research has drawn on theoretical models and clinical observations to develop propositions regarding the mechanisms of diet failure, with only one study examining it directly from the perspective of dieters themselves. Furthermore, research to date has failed to provide an empirically validated, multi-factorial model of diet failure, despite the issue being recognised as a complex and multifaceted one. This study extended on previous research by examining themes of diet failure from the perspective of dieters (n = 22) and health professionals in the field (n = 5).