This is why you're fat: sugar. So goes the mantra of Fed Up, a new documentary that shares a producer with An Inconvenient Truth, as well as a similarly broad, clear message to Americans. Instead of global warming, however, Fed Up takes on another crisis: America's food industry, and the toll it's taking on the health of our society, particularly that of our children. Both efficient and thorough, Fed Up's drive to make its case to even the most oblivious viewer is palpable. by Marjorie Skinner