International expert consensus on definitions and management of weight recurrence and suboptimal response after metabolic and bariatric surgery: a Delphi study

Background: Weight recurrence and suboptimal response after metabolic and bariatric surgery (MBS) lack standardized definitions and management approaches, creating barriers to evidence-based treatment decisions and coordinated care across multiple specialties. Objectives: To establish international expert consensus on terminology, diagnostic approaches, and management strategies for suboptimal response and weight recurrence after MBS. Setting: International Delphi study across multiple countries and health care systems. Methods: A two-round modified Delphi study was conducted with 66 international experts across five specialties (MBS, obesity medicine, gastroenterology, endocrinology, dietetics and nutrition, and psychology). A 164-item questionnaire was developed, spanning seven dimensions: conservative management, diagnostic methods, endoscopic interventions, quantitative thresholds, risk factors, surgical interventions, and terminology. Consensus was defined a priori as ≥70% agreement. Inter-rater reliability was assessed using Gwet's AC1 coefficient. Results: Response rates were 54.5% (Round 1) and 57.6% (Round 2). Consensus achievement improved significantly between rounds (26.2% to 40.9% of items). Experts reached unanimous agreement on core management principles including individualized patient care (100%) and the appropriateness of specialists prescribing antiobesity medications (100%). Strong consensus emerged on standardized terminology with "suboptimal" as the preferred term (89.5%) and %TWL as the optimal measurement approach (94.6). For quantitative thresholds, consensus was achieved on surgical nonresponse defined as <10% TWL at 12 months (73.0%), recurrent weight gain as >25% of lost weight from nadir (70.3%), and a 10% change in %EWL from nadir as normal physiologic response (83.8%). Conservative management items achieved the highest consensus rates (80.9%) while quantitative threshold items require additional research (28.1%). Inter-rater reliability improved across all domains, with conservative management achieving substantial agreement (AC1 = .70). Conclusion: Expert consensus was achieved on fundamental principles of postbariatric care, including preferred terminology, measurement metrics, and provider roles. These recommendations address important gaps in clinical practice standardization.