According to recent studies, about 1/3 of Americans are obese, and between 1998 and 2006, the obesity rate rose 37% in this country. Obesity-related illnesses accounted for an estimated $147 billion in 2008, nearly 10 percent of all U.S. medical spending, according to the Centers for Disease Control. On today’s edition of Please Explain, we're looking into the causes of the dramatic rise in obesity and the health risks that come with it. We're joined by Dr. Louis Aronne, Clinical Professor of Medicine at Weill-Cornell Medical College-NY Presbyterian Hospital, and Director of the Comprehensive Weight Control Program, and Dr. Kelly Brownell, Director of the Rudd Center for Food Policy and Obesity, Yale University.