Samuel Klein, MD, is the Danforth Professor of Medicine and Nutritional Science, and he directs the Center for Human Nutrition, the Center for Applied Research Sciences and the Division of Geriatrics and Nutritional Science at Washington University. He also is the medical director of WUSTL’s Weight Management and Eating Disorders Center. An internationally known expert on obesity and weight loss, Klein was one of the first researchers in the world to critically compare low-fat diets to low-carbohydrate diets. He also has studied metabolic differences in the body that are determined by whether fat tends to be stored under the skin or inside of organs such as the liver. He has compared the potential metabolic benefits of various types of weight-loss surgery and looked at the supposed health benefits of resveratrol, an ingredient in red wine that had been thought to improve metabolic function and help prevent type 2 diabetes.