Bun-free Skinny Burger (photo: Fatburger)

LOS ANGELES – Beef has replaced the buns in Fatburger's new Skinny Burger.

The quick-service chain recently launched a bun-free burger — a 1/3 lb. lean beef patty cut in half with lettuce, tomatoes, cheese and other fixings sandwiched in between the beef.

Andrew Wiederhorn, CEO, told CNBC the Skinny Burger is 320 calories, roughly 250 calories less than a regular Fatburger.