Insulin resistance is a key feature of postoperative metabolism, leading to decreased glucose absorption in adipose tissue and skeletal muscle, with an increased glucose release due to hepatic gluconeogenesis and hyperglycemia. Development of insulin resistance is associated with increased length of hospital stay (LOS), morbidity, and mortality. One of the strategies employed to reduce the postoperative stress response and perioperative insulin resistance includes the reduction of the preoperative fasting time via preoperative carbohydrate oral (CHO) drink. Preoperative carbohydrate intake is an integral part of the Enhanced Recovery After Surgery (ERAS) protocol and previous studies have shown that preoperative carbohydrate loading can increase patient comfort. Although ERAS protocols are increasingly used and implemented in bariatric surgery centres specific components of these protocols, such as preoperative oral carbohydrate nutrition, have not yet been rigorously analyzed.

The aim of this prospective study is to compare the differences in patient outcomes between preoperative CHO loading and a conventional fasting protocol. The secondary aim is to perform a subgroup analysis of Roux-en-Y bypass and sleeve gastrectomy.

Inclusion Criteria:

• Patients who will undergo surgery at the Elective Surgery Clinic of the University Clinical Centre in Gdansk, Poland.

Exclusion Criteria:

• Patients who will be unable or will refuse to express informed concern