I read up a little on the E/C/A stack. It's really interesting how this thing works. My main source for this post is Wikipedia.
Alright, so Ephedrine, the first part of the stack, acts as a beta antagonist and releases noradrenaline into your system. This has serious stimulant effects as it is, but what the noradrenaline also does is act on your white adipose tissue by increasing cAMP levels. (You read about this a lot in modern fat burners) By increasing cAMP, you enter thermogenesis. Your body's core temp. is raised about 2 degrees, and your metabolism increases by about 10%.
Now, at this point, you'd think, hey, why even add the caffeine or aspirin?
Your body is a survival machine. It uses its negative feedback system to normalize your metabolism. Your body doesn't WANT a fast metabolism, because that is not conducive to survival. So what happens is, your body produces two chemicals: phosphodiestarase (in the cells), and prostaglandins (outside the cells).
Enter caffeine. Caffeine inhibits your body's production of phosphodiesterase. So it eliminates half of your body's defense mechanism against the increase in metabolism. But hey, as an added bonus, caffeine bonds with adenosine receptors in your brain, further releasing adrenaline. This, in turn, increases your levels of cAMP, and thus adds to Ephedrine's thermogenic/stimulant effect.
The defense mechanism against fat burning now crippled, the stack delivers the final blow with Aspirin. Aspirin inhibits: you guessed it, prostaglandins. This, along with caffeine, lengthens and preserves the process of thermogenesis.
DAMN that's sweet. Haha. Even if I never take the E/C/A, I think I'll always be pissed that there had to be a crackdown on it. Amazing that shit like this, that could potentially aid our entire fatass country in losing weight, gets banned/regulated, while cigarettes, trans-fat rich fast food, and alcohol are freely sold.