Up to date only a few studies have focused on fat quantification before and after bariatric surgery: patients treated with laparoscopic gastric banding (a purely restrictive procedure) and patients undergoing metabolic surgery such as sleeve gastrectomy and gastric bypass have been examined pre- and postoperatively by means of MRI fat quantification. However, in these studies single voxel spectroscopy was used. In contrast, in this current trial investigators aim to assess full organ volume, which hopefully will provide more accurate data.