Obesity is a multifactorial disease that affects millions of people worldwide. It is the main independent risk factor for developing type 2 diabetes mellitus (T2DM). Most patients with T2DM and glucose intolerance (GI) are overweight, a condition known as diabesity. In patients with the most severe form of obesity, i.e., morbid obesity, the likelihood of developing diseases associated with obesity is increased.

The investigators currently know that bariatric surgery provides sustained weight loss and well-documented remission of T2DM. Patients who undergo bariatric surgery show long-term reduced mortality from coronary artery disease, cancer and diabetes; 136 lives are saved per 10,000 surgical procedures performed. Bariatric surgery is a relatively safe procedure that is becoming increasingly well-accepted; in 2007, approximately 170,000 bariatric procedures were performed in the USA. Currently, bariatric surgery is the most effective choice of treatment of morbidly obese patients with diabetes. The surgical procedures that are currently performed to treat morbid obesity are divided into two main groups: gastric restrictive procedures and combination procedures; the latter combine gastric restriction and malabsorption. The roux-en-Y gastric bypass (RYGB) is the combination procedure most frequently performed, whereas sleeve gastrectomy (SG) is an emerging restrictive procedure. SG can be performed as the first of a two-stage operation in patients at high risk of death, or as a definitive surgical procedure. It has shown good results with regard to weight loss and glycemic control in various studies. The potential advantages of SG include lower probability of vitamin and mineral deficiencies because this procedure has no malabsorptive component; access to the entire intestinal tract; no need for a subcutaneous access port or adjustments; absence of dumping syndrome and lower probability of intestinal obstruction. In addition, SG can be performed in patients who have inflammatory bowel disease or who have undergone bowel surgery, and it can be easily converted into RYGB. Both SG and RYGB can be performed with or without the placement of a Silastic® ring.

The metabolic control achieved with bariatric procedures has been demonstrated and reproduced in various medical centers worldwide. Metabolic control can be achieved with gastric restrictive procedures such as vertical banded gastroplasty, adjustable gastric banding and, more recently, SG. However, it has been shown that glucose homeostasis is affected by various intestinal mechanisms observed exclusively in procedures that include a malabsorptive element, such as RYGB. A systematic review of 22,094 cases of morbidly obese patients submitted to bariatric surgery has shown that resolution of T2DM was achieved in 76.8% of the cases, improvement being achieved in 86% of cases. Among the criteria used to diagnose metabolic syndrome, fasting glucose levels are the first to return to normal in patients submitted to Silastic® ring gastric bypass (SRGB), a modification of the traditional RYGB which consists in adding a Silastic® ring to the gastric bypass operation. Normoglycemia after bariatric procedures, as well as diabesity itself, is multifactorial. Normoglycemia is observed as a result of dietary control, decreased plasma levels of ghrelin, weight loss and reduction of body fat, as well as of the release of gastrointestinal hormones that interfere with the function of pancreatic β cells (incretins).

The main purpose of this study was to compare the weight loss of morbidly obese patients submitted to either a Silastic® ring sleeve gastrectomy (SRSG) or an SRGB, as well as to compare the effects of both procedures on glucose homeostasis in morbidly obese patients.