it seems to work by giving your body negative consequences for eating the wrong foods. If you read all the literature on it, it causes oily anal leakage if your diet has over a very small percentage of fat in it (the exact number eludes me now). So if you take the medicine and eat the right foods, great but if not you have quite unpleasant side effects and that's kind of how most people say they lose the weight. I'm sure theres a specific whatever other reason for it but the people I know who have taken the medicine found the side effect too unpleasant to continue taking it.
i havent tried it, but i heard if you dont stay on track with what you eat then you will have the bad side effects. to me its not worth it.