THIS IS WHY you're fat: sugar. So goes the mantra of Fed Up, a new documentary that shares a producer (Laurie David) 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.

It's wise to focus on health epidemics among youth to address the country's nutrition crisis—a crisis that, as Fed Up notes, is a manifestation of evils that transcend both vanity and the fact that an anti-sugar and anti-processed-food directive is old news in certain (sometimes economically privileged) circles. As the source of Americans' food problems, Fed Up targets the injection of added sugar, in its many guises, into virtually all packaged foods. Sugar consumption can't be canceled out by exercise, and sugar's big-money interests are comparable to the tobacco industry in its heyday.

Both efficient and thorough, Fed Up's drive to make its case to even the most oblivious viewer is palpable. A quick pace prevents it from feeling overlong, though—indeed, there's the sense that the grim statistics and sordid politics are condensed.

The kids Fed Up focuses on—like a tearful 12-year-old girl whose diligent exercise routine isn't working, and a 14-year-old facing gastric bypass surgery—are easy to sympathize with, and through them, Fed Up addresses dangerously pervasive myths, like that whole foods are more expensive than packaged options. The children's stories—combined with hard numbers, a little history, and clips of Honey Boo Boo—invite you to get riled up. By the time the film points out that if a foreign country were perpetrating these ills on us, we would probably go to war, it's enough to make you want to grab a gun. Or a quinoa salad.