it will do both. you cant burn only fat. you can only put the ratio mor in your favor. bcaa's help so does eca. adding a steroid will help a lot more but you will still burn up some muscle and like everything else it is also person dependant so try one way this time and another next time and compare yourself to yourself to find the best method. ricks suggestion sounds good also. ive never done it to say what works better for me.