There was a big "Coca-Cola" sign on the refrigerator, but all it held was bottled water and juice. The menu offered sandwiches on eight-grain bread. The lunch ladies were pushing salad. The cafeteria at the William E. Cottle Elementary School has undergone a nutritious change this year, and Congresswoman Nita Lowey chose it as the setting Friday for an announcement of legislation aimed at battling obesity in children. "The exploding rate of obesity is one of the most serious health issues our nation faces," said Lowey, a Democrat who represents parts of Westchester and Rockland counties. She said the health...