Drugs, diet, or surgery? How treatment type and willpower shape responsibility for weight loss and judgments of the physician and treatment

Introduction Grounded in attribution theory and informed by the perspective on health moralization, this study examined how perceived lack of willpower shapes individuals’ judgments of responsibility for weight loss in individuals with obesity across different treatment methods (diet/exercise, bariatric surgery, and weight loss drugs). The study also investigated how willpower attributions and treatment type shape evaluations of the doctor, including trust, perceived credibility, and treatment acceptance. Methods and measures This study used an experimental vignette design in which the weight loss method (diet/exercise vs. bariatric surgery vs. weight loss drugs) was experimentally manipulated, and perceived lack of willpower was measured. The study included 183 adult participants ( M age = 29.3, SD = 10.98; 133 women). Results The moderation analyses revealed that perceived lack of willpower predicted lower responsibility for weight loss, but this effect was conditional on treatment type and emerged primarily in the weight loss drug condition. Across all conditions, treatment type had a robust effect: pharmacological treatments were consistently associated with lower perceived responsibility, lower trust in the doctor, lower perceived credibility, and lower treatment acceptance than surgery and diet/exercise. Perceived lack of willpower did not influence evaluations of the doctor or treatment. Conclusion These findings suggest that individuals rely on distinct judgment processes when evaluating both patients and treatment providers: responsibility attributions are shaped by dispositional beliefs about willpower, whereas evaluations of doctors and treatments are driven by treatment-related cues of effort and legitimacy. Understanding how treatment framing and beliefs about willpower interact may help clinicians communicate more effectively and foster trust in weight management interventions.