In the present study intestinal, hepatic and pancreatic blood flow and volume are measured using [15O]H2O- and [15O]CO radiotracers and PET-MRI imaging in healthy normal weight volunteers (n = 20, BMI ≤ 27 kg/m2) and in morbidly obese T2DM patients (n = 30, BMI ≤ 35 kg/m2) before and after the bariatric surgery operation. The PET imaging will be performed at fasting state but also separately either during 1) mixed meal solution (MMS), 2) GIP-, or 3) GLP-1-infusion. Also abdominal subcutaneous and visceral adipose tissue, intestinal and hepatic tissue samples will be collected.