David L. Katz, MD, is associate professor of public health, director of the Yale Prevention Research Center, and associate director of nutrition science at the Rudd Center for Food Policy and Obesity at Yale University. Dr. Katz writes a monthly nutrition column for O: The Oprah Magazine and a health and nutrition column for the New York Times syndicate. He lives with his wife, collaborator Catherine S. Katz, PhD, and their five children.