Introduction This study comprises of a series of studies in morbidly obese subjects with type 2 diabetes before and after Roux-en-Y Gastric Bypass surgery (RYGB) and the gastric sleeve procedure, investigating the effect of these surgeries on incretin levels and hepatic insulin sensitivity. The method study (study 2) seeks to validate a better and physiological method to investigate insulin sensitivity in morbidly obese patients.