Samuel Klein, MD, is the William H. Danforth Professor of Medicine, Director of the Center for Human Nutrition, Director of the Center for Applied Research Sciences, Chief of the Division of Geriatrics and Nutritional Sciences, and Medical Director of the Weight Management Program at Washington University School of Medicine in St Louis, Missouri. Dr. Klein earned his doctorate from Temple University Medical School in 1979 and master of science degree in nutritional biochemistry and metabolism from the Massachusetts Institute of Technology in 1984. He completed residency training in internal medicine and a clinical nutrition fellowship at University Hospital in Boston, a National Institutes of Health (NIH) Nutrition and Metabolism Research fellowship at Harvard Medical School, and a Gastroenterology fellowship at Mount Sinai Hospital in New York, New York. He is board certified in internal medicine, gastroenterology, and nutrition. Dr. Klein is past President of the North American Association for the Study of Obesity and the American Society for Clinical Nutrition and inaugural Chair of the Integrative Physiology of Obesity and Diabetes NIH study section. He was elected to the American Society for Clinical Investigation in 1996 and to the American Association of Physicians in 2008. Dr. Klein has had consistent R01 funding from the NIH since 1990 and has published more than 300 papers on nutrition, metabolism, and obesity. He has received numerous awards for his research, including the American Gastroenterological Association (AGA) Miles and Shirley Fiterman Foundation Award in Nutrition, the AGA Masters Award for Outstanding Achievement in Basic or Clinical Research in Digestive Sciences, the Daniel P. Schuster Distinguished Investigator Award in Clinical and Translational Science from Washington University School of Medicine, and The Obesity Society TOPS Research Achievement Award. Dr. Klein’s research activities are focused on understanding the mechanisms responsible for metabolic dysfunction associated with weight gain and obesity and the pathophysiology of nonalcoholic fatty liver disease.