I would not use these products, personally. I've used them before (as well as stronger "uppers") and they are a waste of time, health, and money.
You will quickly develop a dependence on them, but you'll also develop a tolerance as well. Sure, you might lose a little weight in the beginning, but long-term use of them is *terrible* for you. I know that from first-hand experience.
So not only will you feel like crap if you ever stop taking them, whatever weight you lost on them will probably come back and then some.
My humble opinion? Restricted caloric intake and moderate exercise is where it's at.