Well working out and doing cardio are two different things. When you work out a certain area it does burn off fat but it mainly helps you grow stronger muscles. It mainly helps burn fat in whatever area you're workin out. Now when you get to cardio, that's when you start to burn off mainly fat. So for people tryin to lose weight I recommend starting off with walking or a slow jog. Then eventually work your way up to running. Also doing small workouts as well.
There are plenty of different cardio workouts other than running but that seems to be the most effective to me.