Response to glucose tolerance testing and solid high carbohydrate challenge: comparison between Roux-en-Y gastric bypass, vertical sleeve gastrectomy, and duodenal switch.

BACKGROUND: Hyperinsulinemic hypoglycemia is common after Roux-en-Y gastric bypass (RYGB) and may result in weight regain. The purpose of our investigation was to compare the effect of RYGB, vertical sleeve gastrectomy (VSG), and duodenal switch (DS) on insulin and glucose response to carbohydrate challenge.

METHODS: Patients meeting National Institutes of Health criteria for bariatric surgery selected their bariatric procedure after evaluation and education in this prospective nonrandomized study. Preoperatively and at 6, 9, and 12 months' follow-up, patients underwent blood draw to determine levels of fasting glucose, fasting insulin, glycated hemoglobin (HbA1c), C-peptide, and 2-h oral glucose challenge test. Homoeostatic Model Assessment (HOMA)-IR, fasting to 1-h and 1- to 2-h ratios of glucose and insulin, were calculated. Statistical analysis was performed using ANOVA and Student's paired t test. All procedures were performed via a laparoscopic technique at a single institution.

RESULTS: Data from a total of 38 patients (13 RYGB, 12 VSG, 13 DS) were available for analysis. At baseline, all groups were similar; the only statistically significant difference was that DS patients had a higher preoperative weight and body mass index (BMI). All operations caused weight loss (BMI 47.7 ± 10-30.7 ± 6.4 kg/m(2) in RYGB; 45.7 ± 8.5-31.1 ± 5.5 kg/m(2) in VSG; 55.9 ± 11.4-27.5 ± 5.6 kg/m(2) in DS), reduction of fasting glucose, and improved insulin sensitivity. RYGB patients had a rapid rise in glucose with an accompanying rise in 1-h insulin to a level that exceeded preoperative levels. This was followed by a rapid decrease in glucose level. In comparison, DS patients had a lower increase in glucose and 1-h insulin, and the lowest HbA1c. These differences were statistically significant at various data points. For VSG, the results were intermediary.

CONCLUSIONS: Compared to gastric bypass, DS results in greater weight loss and improves insulin sensitivity and glucose homeostasis without causing a hyperinsulinemic response. Because the response to challenge after VSG is intermediary, pyloric preservation alone cannot account for this difference.