1. From the Division of Clinical Pharmacology and Autonomic Dysfunction Center (C.S., I.B.), and Division of Gastroenterology, Energy Balance Laboratory (M.S.B.), Department of Medicine, and Department of Biostatistics (C.Y.), Vanderbilt University School of Medicine, Nashville, TN; Diabetes, Endocrinology, and Obesity Branch (K.Y.C.), Division of Intramural Research/National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD.