Gastric bypass in Type 2 diabetes with BMI <30: weight and weight loss have a major influence on outcomes

Aim To assess factors influencing glycaemic control following gastric bypass surgery in patients with Type 2 diabetes and BMI<30kg/m2. Methods Prospective longitudinal study of 103 patients with inadequate glycaemic control who underwent gastric bypass surgery at Soonchunhyang University, Seoul, Korea (n=66) and Min-Sheng General Hospital, Taipei, Taiwan (n=37). Procedures were performed August 2009 to January 2011. Key outcome measures were excellent glycaemic control of Type 2 diabetes defined as HbA1c <42mmol/mol (6%); inadequate response defined as HbA1c >53mmol/mol (>7%). Analysis was conducted using binary logistic regression, and cut-points obtained from receiver operator characteristics. Results Excellent glycaemic control was achieved in 31 (30%) at 1year. Diabetes duration of <7years and BMI>27kg/m2 provided independent predictors and useful cut-points. Likelihood of excellent glycaemic control for an individual could be estimated using loge (Odds)=6.7+(0.26xBMI)+(1.2xdiabetes duration). Baseline BMI of <27 kg/m2 and baseline C-peptide of <2.0ng/ml, best predicted a poor glycaemic response. In those with favourable baseline characteristics percentage weight loss (%WL) had a dominant influence on glycaemic outcomes. Baseline C-peptide (>2.4ng/ml) and subsequent percentage weight loss (>16%) were associated with excellent glycaemic control. Higher BMI was associated with greater percentage weight loss. Conclusion In patients with Type 2 diabetes and BMI <30 kg/m2, glycaemic response to gastric bypass is predicted by higher baseline BMI, shorter disease duration and higher fasting C-peptide. Post-surgery weight loss has a dominant effect. Baseline BMI and weight loss have a major influence on outcomes.