The academics studied body-fat data from more than 1 million California ninth-graders over an eight-year period, focusing on the proximity of the school to well-known chains including McDonald's, Burger King, KFC, Taco Bell and Pizza Hut. California has banned artery-clogging trans fats, and Los Angeles has a one-year moratorium on new fast-food outlets in a 32-square-mile area of South L.A. More than a dozen states and numerous cities are pondering legislation patterned after a new California law forcing chain restaurants to list calorie counts on their menus.