Fifteen Year Weight, Metabolic, and Conversion Outcomes After Primary Metabolic Bariatric Surgery in Individuals Living with Obesity and Type 2 Diabetes

Background: Metabolic and bariatric surgery (MBS) is an established intervention for weight reduction and metabolic improvement in individuals living with obesity and type 2 diabetes mellitus (T2DM), with well described short term and medium term benefits. However, long term results extending beyond 10 years, particularly in people with T2DM, remain limited. Objective: To evaluate 15 years weight, metabolic and surgical outcomes following primary MBS in individuals living with obesity and T2DM. Methods: This retrospective cohort study included patients with T2DM who underwent primary MBS between 2003 and 2007 at a single tertiary centre. Long term follow up data at approximately 15 years were available for 49 individuals. Primary outcomes included changes in weight, body mass index (BMI), and diabetes related outcomes. Secondary outcomes included medication use, cardiovascular events, and secondary surgical procedures, classified as revisions or conversions according to International Federation for the Surgery of Obesity and Metabolic Disorders definitions. Analyses were descriptive, with paired comparisons performed where data completeness permitted. Results: Fifteen years follow up data were available for 49 individuals with type 2 diabetes mellitus. Median body weight decreased from 143.0 kg to 101.6 kg, and median body mass index (BMI) decreased from 52.6 kg/m² to 39.6 kg/m² (both p < 0.01). Median percentage total body weight loss was 27.5%, and median percentage excess weight loss was 49.0%. Paired HbA1c data were available for 6 patients, with median values decreasing from 8.4% to 5.6%; six patients met criteria for diabetes remission at 15 years. Among 28 patients with medication data, oral hypoglycaemic agent use decreased from 27 to 10 patients (p = 0.01), and insulin use decreased from 6 to 3 patients (p < 0.001). Thirteen patients (26.5%) underwent secondary bariatric procedures during follow up, including 9 conversions and 4 revisions. Conclusions: In this real world cohort of individuals living with obesity and T2DM, MBS was associated with durable long term weight reduction and reduced reliance on glucose lowering medications over 15 years. Secondary surgical procedures occurred in a subset of patients and should be interpreted in the context of baseline patient characteristics and evolving surgical practice. Larger prospective studies with comprehensive long term follow up are required to further define durability and metabolic outcomes beyond a decade.