Obesity and its ensuing metabolic complications such as type 2 diabetes mellitus, are exponentially increasing worldwide. \* \* The most effective treatment for obesity is bariatric surgery. \* Different bariatric procedures are available. In the 1960's, the Roux-en-Y gastric bypass (RYGB) was developed, in which the stomach is divided with staplers to create a small gastric pouch, while the jejunum is divided 30 to 50 cm distal to the ligament of Treitz. The distal limb is then anastomosed to the small gastric pouch and a jejunojejunostomy is performed 50 to 150 cm distal from the gastrojejunostomy. Sleeve gastrectomy on the other hand, reduces the stomach size by vertical stapling. In the 1990's, gastric banding was developed, reducing the volume of the stomach by annular banding. The amount of excess body weight reduction varies among the different techniques, with 60% to 70% reported for RYGB\*, 55% for sleeve gastrectomy\* and up to 65% for gastric banding\*. Worldwide, it is estimated that a total of 344000 procedures were performed in 2008. Roux-en-Y gastric bypass was the most common (47%) followed by gastric banding (42%) and sleeve gastrectomy (5%).\*

In 1987, Pories et al. published data on the stunning observation that 99% of obese patients with type 2 diabetes or impaired glucose tolerance that had undergone Roux-en-Y gastric bypass became and remained euglycemic after surgery.\* Since then, all commonly used bariatric procedures have been shown to restore a normal glucose profile in many diabetes patients. Current data suggest that the bypass procedures are more effective in doing so, with success rates up to 80%,\* than the purely restrictive procedures such as sleeve gastrectomy and gastric banding, with success rates varying between 30% and 70%.\* The improvement in glycaemic control is already seen a few days after surgery, long before any substantial weight loss occurs.

Although different reasons for the rapid amelioration in glycaemic control are discussed in literature, the exact underlying mechanisms are still not understood. In the restrictive procedures, the effect is thought to be mainly mediated by caloric restriction and the ensuing reduction in body weight and improvement in insulin resistance.\* The malabsorptive procedures, such as RYGB, offer different explanatory possibilities. In the so-called 'fore-gut hypothesis', it is suggested that the exclusion of the duodenum and proximal jejunum may reduce insulin resistance. \* The 'hind-gut hypothesis' on the other hand, suggests that it is the altered delivery of nutrients to the distal small bowel that causes exaggerated responses of the gut hormones. These gut hormones act as anorectic agents and as incretins that stimulate the beta cells in the pancreas to restore normal first phase insulin response. \*

Most studies to investigate the alterations in glucose metabolism are performed weeks to months after surgery. There are limited data on the evolution of blood glucose in the first days and weeks after RYGB.\* However, to our knowledge, no such data exist on the glycaemic control immediately after sleeve gastrectomy and gastric banding. With the present study we document the evolution in glycaemic control immediately after RYGB, sleeve gastrectomy and gastric banding in type 2 diabetic subjects.