Alli

You mean this:
http://angryjogger.com/my-alli-diet-pill-horror-story-when-my-bowels-failed-me-after-4-pints-of-guinness.html
http://www.nbcnews.com/id/19587389/ns/health-diet_and_nutrition/t/diet-pills-icky-side-effects-keep-users-honest/
http://www.blogher.com/alli-diarrhea-diet

It "works" but has horrible side effects. Most people are strongly opposed to pooping themselves in public.

I tried it once, and unless you like staying close to a bathroom, I'd avoid Alli altogether. If you eat more than 15 grams of fat per meal you will have some nasty side effects. Read about them in this article:

http://www.thewvsr.com/alli.htm

I've heard really bad things about Alli. It literally forces you not to eat fats by the horrifying repercussions if you do. And fat isn't bad for you unless you eat too much of it and it causes you to eat more calories than you're burning.

Count calories, eat what you like as long as it fits into your goals and save your money.

A family friend started it for some reason while on vacation. White clothes and too much fat in the food. . . Terrible combo.