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 Örebro 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.