Fatty liver in the obese is a common finding; some cases develop steato-hepatosis which in the long-term can lead to liver cirrhosis. The effect of bariatric surgery on fat distribution in the liver has so far been studied with liver biopsies and single voxel MR techniques. With this trial investigators present a new, whole organ MR-quantification of liver fat and describe changes after bariatric surgery in visceral and subcutaneous fat.