Background: Diabetes surgery in nonobese or moderately obese patients is an emerging topic. The identification of preoperative factors predicting diabetes outcome following bariatric surgery, especially for metabolic nonresponders, is imperative.
Methods: Between 2005 and 2011, 235 patients underwent bariatric surgery for morbid obesity. Eighty-two of 235 patients had type 2 diabetes mellitus (T2DM). Data from this subgroup were investigated with univariate and multivariate analyses to identify predictors for metabolic nonresponse after surgery.
Results: Diabetes did not improve in 17/82 patients within 3 months after surgery. No correlation between excess body weight loss and metabolic response was detected. In univariate analysis, preoperative duration of diabetes was significantly longer in the nonresponder group (9.146 vs. 6.270 years; *p = 0.016), preoperative HbA1c levels were significantly higher among the nonresponders than among the responders (8.341 vs. 7.781 %; *p = 0.033), and more patients in the nonresponder group were reliant on a multi-drug approach preoperatively (*p = 0.045). In multivariate analysis, age, preoperative doses of insulin, and preoperative oral antidiabetics showed positive correlation to metabolic nonresponse after surgery (*p = 0.04; *p = 0.021; *p = 0.021). Metabolic failure rate was lower after Roux-en-Y gastric bypass compared to other bariatric procedures (**p = 0.008).
Conclusions: A long history of preoperative T2DM, high preoperative HbA1c levels, and a preoperative therapy consisting of diverse approaches to diabetes treatment may be factors predicting failure of diabetes improvement in the early postoperative course after bariatric surgery. Age, preoperative insulin, and oral antidiabetic medication can be regarded as independent, significant predictors for metabolic outcome after bariatric surgery.