Dr. Walter Willett is Professor of Epidemiology and Nutrition at the Harvard T.H. Chan School of Public Health and Professor of Medicine at Harvard Medical School. He served as Chair of the Department of Nutrition at Harvard for 25 years.  His work has focused on the development of methods, using both questionnaire and biochemical approaches, to study the effects of diet on the occurrence of major diseases. He has applied these methods to large cohort studies, including nearly 300,000 men and women, that are providing the most detailed information on the long-term health consequences of diets.  Dr. Willett has published over 2,000 articles, primarily on lifestyle risk factors for cardiometabolic disease and cancer, and has written the textbook, Nutritional Epidemiology. He is a member of the National Academy of Medicine.