nope it doesnt, or isnt supposed too, you will feel like you are on ephedra because it makes your receptors twitch, (giving you the jitters), but in turn all of those little receptors twitching constantly need energy to keep twitching therefore burning more calories,
i have read somewhere that ephedra raises your metabolism by 3%, clenbuterol raises it by 10%, t3 raises your metabolism by 20%, but taking clen and t-3 together raises it to 30%, i forgot where i read that at though, it has been a couple months
the only thing stronger is DNP, which is something from dynomite and is very very unsafe,
i have used clen for 6 weeks, 2- 2 week cylces and i went from a 44" waist to 36" waist in a month and a half, so it does good with proper diet and cardio, just becareful of your heart rate while doing cardio while on clen