A health paradox exists in America. People here are more obsessed with fitness and exercise than ever before. You can drive by gyms and see all the people inside, not to mention all the people out for walks and runs. Then, there are the yoga studios and spin classes. You get the idea. 

But yet, the country has never been more unhealthy. Obesity rates are soaring which is creating all kinds of medical issues. A new book explores this paradox and why it exists. It's called Fit Nation: The Gains and Pains of America's Exercise Obsession. With us is the book's author, Natalia Mehlman Petrzela. She's a historian at The New School as well as a fitness instructor.