Type 2 diabetes mellitus (T2DM) is an established risk factor for cardiovascular diseases. The rising prevalence of obesity is increasing the burden of this disease and consequently of cardiovascular mortality. In retrospective series, improvement in glycemic control in obese patients with T2DM has been related to weight loss after bariatric surgery. Prospective data regarding resolution of T2DM after gastric bypass surgery (GBS) have been scant. Therefore, the aim of our study was to analyze the efficacy of the GBS in reversing T2DM in a prospective cohort of morbidly obese patients.

Methods:
Morbidly obese patients with T2DM undergoing laparoscopic GBS were enrolled in the study. Diagnosis of T2DM was made according to WHO criteria. Patients underwent assessment of fasting glucose, glycosylated hemoglobin (HbA1C), lipid profile, and waist circumference measurements at baseline and 6-month after surgery. Logistic regression was used in both univariate and multivariate modeling to identify independent variables associated with complete resolution of T2DM. Complete resolution of T2DM was defined by normal levels of fasting plasma glucose and HbA1C after discontinuing medical treatment.

Results:
The study enrolled 50 consecutive patients. Six months after surgery, fasting plasma glucose decreased from a preoperative mean of 161±50 mg/dL to 108±33 mg/dL (P=0.001) and HbA1C decreased from a preoperative mean of 7.5 ± 1.6 % to 6.2 ± 1.2 (P=0.001). Resolution of T2DM was achieved in 35 (70%) patients (full response). The remaining 15 patients decreased the daily medication requirements (partial response). On univariate analysis, preoperative variables associated with resolution of T2DM were: waist circumference <127 cm inches (P<0.001), and absence of insulin treatment. Waist circumference and treatment without insulin remained significant predictors of T2DM resolution after GBS in the multivariate logistic regression model after adjusting for covariates. Waist circumference <127 cm increased 40 times the chance to have T2DM resolution after GBS (OR 40.4; 95% CI 4.6-352; P=0.001). Absence of insulin treatment increased 9 times the chance to have resolution of the T2DM after GBS (OR 9; 95% CI 2.2-36.5; P=0.002).

Conclusion:
Gastric bypass surgery significantly reduces the prevalence of T2DM. Peripheral fat distribution (smaller waist circumference) and absence of insulin treatment were independent and significant predictors of complete resolution of the T2DM.