 The majority of the research subjects will be recruited from the Yale Pediatric Obesity Clinic and the Endocrine Clinic. Following the oral glucose tolerance test OGTT:normal glucose tolerant if plasma glucose at two hours is 140 mgdl and impaired glucose tolerant if plasma glucose is 140 mgdl. All subjects must be in good general health, have a normal medical history and physical exam, and have no endocrinopathies or other diseases that might affect glucose metabolism. They will not be on any medications that are known to alter glucose or insulin metabolism or certain psychiatric medications. Subjects determined to be eligible will receive a MRI to determine Hepatic Fat Content. Subjects will agree to genetic testing to determine genotype. 