My experience with fat burners is (commonly known around here as ECA's), they burn fat and help you to lose weight but generally you don't bulk up on them. It really depends on how much muscle you already have, and how much weight and fat you have to lose.

What I recommend not doing is, fat burners and creatine. They counteract each other. Keep doing 40 minutes of cardio a day, and you can keep your carbs low until your bf, and weight start getting low. Then you may have to increase carbo's so you'll have strength and endurance. I'm also making an assumption that you're resistance training too, and not just doing cardio.