Background Preoperative attrition is highly prevalent in patients referred for bariatric surgery. Little information is available neither on reasons reported by patients for attrition in knowledge nor costs of attrition in a publicly funded health system. Objectives To assess the reasons for the attrition of bariatric candidates and calculate its economic impact on a population with obesity in a public hospital in France. Methods This is a retrospective study including all bariatric surgery candidates between 2014 and 2018 in our Center of Excellence in Obesity Care. Data were extracted from the hospital information system, and patient-related outcomes were collected via a standardized questionnaire. Economic analysis was performed. Primary outcome was to analyze the rate of preoperative attrition. Secondary outcome was reasons for discontinuation and their economic impact. Results In total, 1360 patients were referred for bariatric surgery at our hospital, and 1225 were included in the study. Attrition rate in preoperative phase was 46.8%. Three factors were significantly associated with follow-up fragmentation risk: unemployment (OR 0.52, 95% CI 0.29–0.7, p < 0.001), active smoking (OR 2.24, 95% CI 1.53–5.15, p < 0.001), and body mass index (OR 0.98, 95% CI 0.97–1.00, p = 0.036). Average cost to the healthcare system was €792 for each patient who dropped out. Conclusions We identified predictors and patient-reported factors that seem to be beyond the possibility of removal by health professionals. We should consider and address preventable factors, through the development of care pathways tailored to the individual profile of a patient. Graphical Abstract