The Importance of Caloric Restriction in the Early Improvements in Insulin Sensitivity After Roux-en-Y Gastric Bypass Surgery: Response to Ozer, Abdelnour, and Alva

We thank Ozer, Abdelnour, and Alva (1) for the recognition of the importance in understanding the immediate metabolic effects of Roux-en-Y gastric bypass (RYGB) surgery. Although our study (2) was not designed to test the effects of type 2 diabetes or degree of obesity on glucose metabolism immediately post-RYGB, these questions are of considerable interest given the proposition that bariatric surgery be performed to treat type 2 diabetes in subjects with a BMI ≤35 kg/m² (rev. in 3). We encourage investigators to use varied study designs and subject populations to help reach a consensus on how caloric restriction and weight loss impact glucose metabolism.

The following are responses to specific inquiries on the details of the study. Patients were selected to participate in the surgical arm if they had approval for RYGB, no prior gastric operations, and normal liver and kidney function. Patients were excluded from participation if they had an intercurrent infection, currently used anticoagulants, had a history of ketoacidosis or current metabolic acidosis, or had a positive pregnancy test. Requirements for the caloric restriction arm were the same except for approval for RYGB. The average surgery duration was 174 ± 38 min, with three laparoscopic and six open surgeries, and no postoperative complications. In the RYGB group, the five subjects with type 2 diabetes were all treated with single or combination oral antidiabetic agents (metformin, thiazolidinediones, or a sulfonylurea), and one subject was additionally on insulin. In the diet group, the four subjects with type 2 diabetes were also treated with single or combination oral antidiabetic agents (metformin, thiazolidinediones, or a meglitinide), and one subject was additionally on insulin.

We understand the concern of Ozer et al. related to whether the outcome measurements of the study were done in a blinded manner. It is important to note that all sample analyses were performed in a blinded manner; however, it is very difficult to blind investigators who are involved with the care of the patients to group assignment when one group is in the immediate postsurgical period and the other group did not have surgery.