It is actually better to lift weights before doing cardio. Weight lifting before cardio allows the body to burn through its stored sugar source. Once the body has used up all of its sugar energy source, it will being to burn fat. This is simply because fat is the bodies back up energy source, so it is what the body turns to once the sugar energy has been used up. Therefore, weight lifting before cardio allows you to workout harder and with more energy and then once you get to your cardio workout, you will be burning off that stored fat.