Participants also undergo a dual energy x-ray absorptiometry (DEXA) scan to determine lean body mass and a magnetic resonance imaging (MRI) scan of the abdomen to determine liver size. For the DEXA scan, the subject lies still on a table for about 30 minutes while the whole body is scanned using a small amount of radiation. For the MRI, the subject lies in a narrow metal cylinder (the scanner) about 30 minutes for the scan.