Thomas A. Wadden, PhD, is Professor of Psychology at the University of Pennsylvania School of Medicine, where he is also Director of the Weight and Eating Disorders Program. He received his AB from Brown University and his doctorate in clinical psychology from the University of North Carolina at Chapel Hill. Dr. Wadden has published over 150 scientific papers and is the coeditor of two books. He has investigated the treatment of obesity by several methods, including behavior modification, very-low-calorie diets, exercise, pharmacotherapy, and surgery. He serves on the National Task Force for the Prevention and Treatment of Obesity and on the Council of the North American Association for the Study of Obesity. Albert J. Stunkard, MD, is Professor of Psychiatry at the University of Pennsylvania School of Medicine, where in 1957 he founded the Obesity Research Group (now the Weight and Eating Disorders Program). He received his BS from Yale University and his MD from Columbia University. Dr. Stunkard is the author of nearly 400 publications, primarily in the field of obesity, and his research has been supported for 40 years by the National Institutes of Health. He is a member of the Institute of Medicine and serves on the editorial boards of seven journals in the fields of nutrition and behavioral medicine.