I used to work in the supplement business, not in research or anything fun like that, but from what I have seen and heard and read from various reports (some independent) and such is limited, but may be useful.
GNC is really expensive. I don't buy supplements there because I am a poor grad student. Online can be useful.
But here are some supplements that people think help them loose weight.
Cayenne pepper: a thermogenic that is supposed to increase the amount of fat burned. It is a great supplement for a ton of reasons, this may not be one of them.
Yerba Mate, Guarana, cola: These herbs are supposed to give you boundless energy. Some bodies would actually like to take guarana and cola off the market. Yerba Mate is a fine coffee substitute, but I don't think any of these will help you lose a pound.
Ginseng: Extracts in alcohol are awesome. They come in small glass bottles. It may taste like poison and go down like gin, but for the next three hours you will be wired. And this extra energy means more calories burned. It is a young man's herb though, as it isn't recommended for those over 50 or those with a family history of heart conditions. I love it.
B-vitamins. B-12 in particular is a source of energy, but B-vitamins are also essential for a good mood. I don't know about you, but when depressed I don't want to work out; I want to eat junk food, drink like a sailor, and get a little chubby. A multi-vitamin (Nature's Way Alive is my favorite, a balance of quality and price)is a smart idea anyway and will have more than enough B.
Chromium: When you eat food it turns into blood sugar. Blood sugar is either used as energy or turned into fat. If you take chromium it slows down blood sugar metabolization. Which means it is around to be used as energy (yay!) and not converted to fat as quickly. It is in the above mentioned multi.
Things like Hoodia or apple cider vinegar are most likely snake oil.
So, to sum up, multi-vitamin good, everything else, probably not so good.
thanks for reading.