Ephedra is actually an over the counter herbal supplement that comes in products like Metabolife, Xenadrine, and Ripped Fuel. When you get it in these products it's called Ma-Huang (spell?) which is simply the naturally occurring form of ephedra.
The reason guys take it is because it increases your metabolism quite a bit and causes you to burn fat like nothing [legal] out there. The reason it does this however, is due to the fact that it speeds up your heart rate, accelerates your blood pressure, and essentially causes your body to go into fast forward so thing just burn off.
The problem therein lies in the fact that when everything speeds up like that, your body goes into somewhat of a "fight of flight†mode where things start working much differently due to the fact that endorphins are released(I'm not going to go into how all of this works since it would take forever.) By taking epedra you are overloading your body with with chemicals which can cause the body to literally shut down, which inevitably causes death. Other side effects are: stroke, heart attack, tachycardia (accelerated heart rate), hypertension, and the big one, permanent and irreversible penile dysfunction!!! (willy don't work no' mo')
Finally, if all that weren't enough, just so you know exactly what epedra really is, it's the precursor chemical to meth-amphetamine. So when anyone takes this stuff they are literally taking a lower dose of a highly addictive and exceptionally dangerous chemical, and for any of us that have ever had to deal with tweakers (the common term for speed addicts) you know that this is something you would never want to be, or be associated with.
I'm really glad a major organization in the U.S. finally took a stand on this crap. Canada has already banned it, and I can't understand why the FDA allows it to continue to be sold over the counter to anyone- including kids- who walk up and want to buy some.