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 Director of the Weight Management Program at Washington University School of Medicine in St. Louis, Missouri.

Dr. Klein received an MD degree from Temple University Medical School and an MS in Nutritional Biochemistry and Metabolism from the Massachusetts Institute of Technology. He completed residency training in Internal Medicine and a Clinical Nutrition fellowship at Boston University Hospital, a Nutrition and Metabolism Research fellowship at Harvard Medical School, and a Gastroenterology fellowship at The Mt.Sinai Medical Center. 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. He was 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 published more than 400 papers in nutrition, metabolism, and obesity. His research activities focus on understanding the mechanisms responsible for metabolic dysfunction associated with obesity, NAFLD, and the therapeutic effects of weight loss.