The development of a valid easy procedure that estimates insulin sensitivity at the same time the effect of the incretin hormones can be studied is of great value in especially RYGB operated patients where the secretion of hormones has been altered by the procedure. Understanding the impact of incretin hormones and hepatic insulin resistance on glucose intolerance may have implications for the medical treatment of obese patients, and may potentially predict which subset of patients are likely to experience the greatest benefits of RYGB or gastric sleeve surgery.