Is Burger King’s Big Mac Clone Stealing McDonald’s Lunch Money?

It’s just a small improvement, but Burger King’s same-store sales increased 0.1 percent in the U.S. and Canada during the first quarter—welcome news after falling 0.9 percent in 2013. The bump, Burger King says, was driven in part by its new Big King sandwich, which recently became 0.8 ounces larger than the incredibly similar, original two-beef-patty champion, the Big Mac. In fact, Burger King is so bullish about the Big King that it’s added a chicken version called the Chicken Big King.

Now McDonald’s must defend its big-burger turf, which is essential at a time when fast-food chains are also losing customers to fast-casual competitors such as Chipotle Mexican Grill and Panera Bread. Some McDonald’s restaurants, for instance, are offering buy-one-get-one Big Mac promotions.