Conversion from Prediabetes to Diabetes in Individuals with Obesity, 5-Years Post-Band, Sleeve, and Gastric Bypass Surgeries

Background: Identifying risk factors for conversion to diabetes among individuals with obesity and prediabetes is important for preventing diabetes. Purpose: We assessed conversion rates to diabetes 5 years after three types of metabolic surgery and examined predictors of diabetes development. Methods: We accessed data of individuals with prediabetes, defined as fasting glucose (FG) 100–125 mg/dL (5.6–6.9 mmol/L) or HbA1c 5.7–6.4% at baseline (preoperatively), who underwent metabolic surgeries in Clalit Health Services during 2002–2011. Results: Of 1,756 individuals with prediabetes, 819 underwent gastric banding (GB), 845 sleeve gastrectomy (SG), and 92 Roux-en-Y gastric bypass (RYGB). Mean age was 41.6 years and 73.5% were women. Five years post-surgery, 177 (10.1%) had developed diabetes. Conversion rates by type of surgery were 14.4%, 6.3%, and 6.5% for GB, SG, and RYGB, respectively (p < 0.001). Conversion was more rapid following GB than SG or RYGB (χ²(2) = 29.67, p < 0.005). In a multiple-logistic-regression model, predictors of diabetes development 5 years postoperatively were (1) weight loss during the first postoperative year and (2) preoperative levels of both FG and HbA1c within the prediabetes range. Baseline weight, age, and sex, were not associated with conversion to diabetes. Conversion rates were lower (4.7%) five years postoperatively for patients who lost > 25% of their baseline weight, compared to those who lost less than 15% of their weight during the first postoperative year: (14.0% < 0.001). Conclusions: Our findings emphasize the importance of preoperative glycemic control and weight loss during the first year postoperatively, for the long-term prevention of diabetes in patients with prediabetes undergoing metabolic surgery.