Coca-Cola, the world’s largest maker of sugary sodas, is under fire for giving millions of dollars to a group of scientists who say that lack of exercise is much more important cause of obesity than poor diets. Are they right?  Is Coke using scientists to reverse the recent decline in soda sales? And what are the best ways to solve America's obesity crisis? Kelly Brownell, Dean of the Sanford School of Public Health at Duke University, is our guest.