How many times a week do you eat corn? Try 50. Self-interested moves from farmers, producers and government officials have made corn and its children (corn starch and corn syrup) the staple of the American diet. It’s cheap, it’s filling and it’s changing human bodies faster than the prehistoric trek out of Africa. Robert Kenner’s documentary tracks how big business has warped our food. This isn’t a conspiracy thriller, but an indictment of all the tiny decisions made for the bottom line that add up to fat children and skyrocketing rates of diabetes. Talking heads Michael Pollan (The Omnivore’s Dilemma) and Eric Schlosser (Fast Food Nation) throw their weight behind this engaging and enraging primer of corporate caloric misdeeds as Kenner skips around from chickens to pigs to spinach to potatoes. Even the bacon-loving (myself included) left the theater vowing to eat more organic. But Kenner smartly makes it clear that choosing to eat better is a luxury. In one scene, he takes a poor and overweight family living off dollar menus to the grocery store to see what healthy, filling choices their budget affords. A crown of broccoli costs a cheeseburger and a half, sighs the dad, as the youngest girl, already weighed down by cheap calories, looks wistfully at some too-pricey pears. But the business model that allows a fried chicken sandwich to cost less than a grapefruit at Whole Foods will exist until shoppers make the choice to make selling junk food economically unsustainable. After all, the one upside to having our food supply run by only a handful of corporations is that they can just as easily promote salads if that’s where the money is. Notes a dairy producer, food might be the one area where buying healthy from Wal-Mart might serve a long-term good. The more free-range eggs Sam Walton’s family sells, the more they’ll order—meaning more and more chickens get to stretch their wings.