Inclusion criteria:  Morbidly obese group  BMI 35.0-45.0 kg/m2, or BMI 32.0-45.0 kg/m2 and diagnosed diabetes Age 18-60 years Eligible to bariatric surgery evaluated according to normal treatment paradigm  Non-obese controls  BMI 18-27 kg/m2 Age 18-60 years Fasting plasma glucose ≤6.1 mmol/L Normal values in 2-hour oral glucose tolerance test  Exclusion criteria:  Morbidly obese group  Metal objects in the body (including pacemakers, metallic artificial valve prostheses, inner ear implants, surgical clipses, braces, foreign fragments) Previous participation in PET studies Pregnancy Poor compliance, alcohol or drug abuse Weight over 150 kg or waist circumference over 150 cm Diabetes with fasting glucose levels ≥7.0 mmol/L, or treatment with insulin Any chronic disease, medication or condition that could create a hazard to subject safety, endanger study procedures or interfere with the interpretation of results.  Non-obese controls  Metal objects in the body (including pacemakers, metallic artificial valve prostheses, inner ear implants, surgical clipses, braces, foreign fragments) Previous participation in PET studies Pregnancy Poor compliance, alcohol or drug abuse Smoking History of eating disorders, drastic weight-gain or weight-loss History of psychiatric disorders Any chronic disease, medication or condition that could create a hazard to subject safety, endanger study procedures or interfere with the interpretation of results