Abnormal glucose tolerance testing after gastric bypass

Background: Symptoms secondary to dumping have been suggested to help patients refrain from simple carbohydrate ingestion after Roux-en-Y gastric bypass (RYGB). During follow-up examinations, we noted many patients with weight regain complaining of fatigue shortly after eating. Thus, we decided to study the glucose tolerance test (GTT) results in a cohort of post-RYGB patients. Methods: A total of 63 RYGB patients, >6 months postoperatively, were studied with a GTT and measurement of insulin levels. The mean age was 48.5 ± 10.8 years, mean preoperative body mass index was 49.0 ± 6.5 kg/m ², mean percentage of excess body mass index lost was 64.5% ± 29.0%, mean weight regain at follow-up was 11.6 ± 12.4 lb, and mean follow-up period was 47.9 months. Results: Of the 63 patients, 49 had abnormal GTT results. Of the 63 patients, 6 were diabetic; however, only 1 of these patients had an elevated fasting glucose level. All 6 patients were diabetic preoperatively. Of the 63 patients, 43 had evidence of reactive hypoglycemia at 1-2 hours after the glucose load. Of these patients, 22 had a maximum/minimum glucose ratio >3:1, including 7 with a ratio >4:1. Conclusion: The results of the present study have demonstrated that an abnormal GTT result is a common finding after RYGB. Reactive hypoglycemia was found in 43 of 63 patients, with insulin values that do not support nesidioblastosis. It is our hypothesis, that rather than preventing simple carbohydrate ingestion, the induced hypoglycemia that occurs might contribute to weight regain and maladaptive eating in certain post-RYGB patients.