Dr. Walter Willett is a physician and epidemiologist and professor of epidemiology and nutrition at the Harvard T.H. Chan School of Public Health. He served as chair of the Department of Nutrition at Harvard for 25 years. Much of his work has been 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 published over 2,200 research papers, primarily on lifestyle risk factors for heart disease and cancer, and has written the textbook, Nutritional Epidemiology. He also has four books for the general public. He is a member of the National Academy of Medicine and the recipient of many national and international awards for his research. (Cambridge, MA)