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

To assess factors influencing glycaemic control following gastric bypass surgery in patients with Type 2 diabetes and BMI<30 kg/m(2) . 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 <42 mmol/mol (=6 ); inadequate response defined as HbA1c > 53 mmol/mol (> 7 ). Analysis was conducted using binary logistic regression, and cut-points obtained from receiver operator characteristics. Excellent glycaemic control was achieved in 31 (30 ) at 1 year. Diabetes duration of <7 years and BMI > 27 kg/m(2) provided independent predictors and useful cut-points. Likelihood of excellent glycaemic control for an individual could be estimated using loge (Odds) = -6.7 + (0.26 - BMI) + (-1.2 ? diabetes duration). Baseline BMI of <27 kg/m(2) 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 (> 2.4 ng/ml) and subsequent percentage weight loss (> 16 ) were associated with excellent glycaemic control. Higher BMI was associated with greater percentage weight loss. In patients with Type 2 diabetes and BMI <30 kg/m(2) , 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.