It not depends on the fat burner. They are helping your body to utilize more fat as energy. Its about the diet. You cant really burn fat and build muscle at the same time, maybe if you are just starting to work out or you worked out before and lost muscle so you have muscle memory to help build it back.
You can try the Anabolic Diet if you want to keep your muscle mass and lose fat as a natty, it works very well for me, but maybe doesnt for you, we are all different. There is a thread about this diet in this section, search for it if you are interested.