Morgan Spurlock got the idea for "Super Size Me," a documentary about what happens when you eat only at McDonald's for a month, after hearing about two obese teenagers who sued the fast food company. They contended McDonald's hid the health risks of its foods. Something clicked, and Spurlock, the creator of MTV's "I Bet You Will," made a bet of sorts with himself. He'd eat every meal at the Golden Arches, sampling everything on the menu, from Big Macs to vanilla shakes, and turn it into his first feature film. Like most Americans, the formerly fit director would quit...