The Effect of Laparoscopic Gastric Bypass Surgery on Insulin Resistance and Glycosylated Hemoglobin A1c: a 2-Year Follow-up Study

Background Bariatric surgery improves insulin sensitivity and secretion in patients with type 2 diabetes, but the effect on patients with prediabetes or even normal glucose tolerance deserves further consideration. Methods Cohort study including patients operated with laparoscopic Roux-en-Y gastric bypass surgery (LRYGB) between November 2012 and June 2017 at the orebro University Hospital (n = 813) with follow-up of 742 patients 2 years after surgery. Fasting insulin, glucose, glycosylated hemoglobin (HbA1c), and homeostatic model assessment of insulin resistance (HOMA-IR) were analyzed at baseline and 2 years after surgery for patients with overt type 2 diabetes, prediabetes, or non-diabetes. Results Fasting insulin levels improved for all groups (diabetics baseline 25.5 mIU/L, IQR 17.5-38.0, 2 years 7.6 mIU/L, IQR 5.4-11.1, p < 0.001; prediabetics baseline 25.0 mIU/L, IQR 17.5-35.0, 2 years 6.7mIU/L, IQR 5.3-8.8, p < 0.001; non-diabetics baseline 20.0 mIU/L, IQR 14.0-30.0, 2 years 6.4 mIU/L, IQR 5.0-8.5, p < 0.001). HbA1c improved in all groups (diabetics baseline 56 mmol/mol, IQR 49-74 [7.3%, IQP 6.6-8.9], 2 years 38 mmol/mol, IQR 36-47 [5.6%, IQR 5.4-6.4], p < 0.001; prediabetics baseline 40 mmol/mol, IQR 39-42 [5.8%, IQR5.7-6.0], 2 years 36 mmol/mol, IQR 34-38 [5.5%, IQR 5.3-5.6], p < 0.001; non-diabetics baseline 35 mmol/mol, IQR 33-37 [5.4%, IQR 5.2-5.5]; 2 years 34 mmol/mol, IQR 31-36 [5.3%, IQR 5.0-5.4], p < 0.001). HOMA-IR improved in all groups (diabetics baseline 9.3 mmol/mol, IQR 5.4-12.9, 2 years 1.9 mmol/mol, IQR 1.4-2.7, p < 0.001; prediabetics baseline 7.0 mmol/mol, IQR 4.3-9.9, 2 years 1.6 mmol/mol, IQR 1.2-2.1, p < 0.001; non-diabetics 4.9 mmol/mol, IQR 3.4-7.3, 2 years 1.4 mmol/mol, IQR 1.1-1.9, p < 0.001). Conclusion Insulin homeostasis and glucometabolic control improve in all patients after LRYGB, not only in diabetics but also in prediabetics and non-diabetic obese patients, and this improvement is sustained 2 years after surgery.