Metabolic bariatric surgery pays off: a longitudinal analysis of weight loss and HbA1c changes in real-world patients data in the West of Scotland

Rationale: The long-term trajectories of weight loss and glycemic outcomes for patients who undergo bariatric surgery remain underexplored, particularly when comparing individuals who undergo surgery to those who are eligible but do not proceed after referral.

Methods: This retrospective cohort study examined 411 patients with type 2 diabetes and obesity who were referred for consideration of metabolic bariatric surgery (MBS) at University Hospital Ayr, Ayrshire & Arran, between January 2009 and December 2020. The primary outcomes were change in percentage total weight loss (%TWL) and Glycosylated Hemoglobin (HbA1c) from baseline to five years.

Results: Of the 411 patients included, 225 (54.7%) did not undergo bariatric surgery. There were no significant differences between the surgery and non-surgery groups with respect to age, BMI or sex. 260 (63%) of the patients were female, the mean age of patients was 48.3 years (SD=8.5), and the mean BMI was 47.4 kg/m² (SD= 7.9). At five years, patients who underwent surgery maintained a 22.0% TWL reduction compared to 8.6% in the non-surgery group (p < 0.001). HbA1c decreased by 1.0% (95% CI: -1.31, -0.70) in the surgery group but increased by 0.4% (95% CI: 0.09, 0.71) in the non-surgery group. Adjusted mixed-effects modelling showed the annual HbA1c level decreased by 0.13% (95% CI: -0.18, -0.07; p < 0.001) in the surgery group, compared to an increase of 0.11% (95% CI: 0.05, 0.17; p < 0.001) in the non-surgery group. %TWL decreased by 1.31% per year (95% CI: -1.73, -0.88; p < 0.001) in the surgery group, while the non-surgery group experienced an increase of 1.11% (95% CI: 0.66, 1.55; p < 0.001).

Conclusion: Patients eligible for MBS who proceed with surgery achieve superior weight loss and glycaemic control compared to those who decide not to proceed with surgery. Opting out of surgery may have significant health implications, highlighting the need for alternative interventions such as intensive lifestyle modification, pharmacotherapy, and diabetes education programs for those unable or unwilling to undergo MBS.