I managed to lose 44lbs last year in 7 months after being diagnosed with diabetes type II and being prescribed xenical.
I must say the side effects were rather unnerving at first if i had eaten too much fat. But i think they partly work because you are so scared of defecating yourself that you daren't eat too much unhealthy food.
I sort of gave up taking them regularly and have put all that weight back on. So as of tomorrow i am on a calorie controlled diet and taking xenical regularly again. Here's hoping!