 Subjects will report to MGH or MIT Clinical Research Center after an overnight fast. Each subject will undergo a history and physical exam to assess for safety and compliance. Blood work, a urine pregnancy test and 24 hour food recall will be collected, identical to that on Day 1 visit. Anthropomorphic measurements will be the same as the Day 1 visit. Subjects will undergo an intravenous glucose tolerance test IVGTT identical to that on the Day 1 visit. Subjects will undergo a DEXA, bioelectric impedance analysis BIA, and CT, and indirect calorimetry identical to those on the Day 1 visit. No study drug will be administered at this visit. 