ok, first off, no direct advice on xenadrine efx.
but, when i used to be a gym rat, there were some guys who were on it. the bottom line, they said was that it gave them some energy but did very little to nothing for fat loss. but, of course, if you do some cardio with it, and it gives you more energy and you can do more cardio.. you see what i'm saying?
i used to imbibe those energy drinks at the gym and would get totally wired. in fact, one time i was convinced i was having a heart attack. good stuff! well, i stopped those but started drinking Red Bull lately in lieu of coffee and i have enjoyed it. but, the buzz does not last very long - maybe two hours for me. the gym drinks were made by american body building and another company i cannnot remember. names like adrenalyn stack and speed stack (which used to contain ma huang before they banned it). the ma huang and bitter orange extract will give you a buzz, but a very nervous one at that.