Alli works by causing fat malabsorption- something that many Crohnies already have problems with. On their website, they tell you that loose, uncontrollable stools are a "treatment effect" and suggest you wear dark pants and bring an extra change of clothes to work. No lie.
Having worked in the weight loss industry (Jenny Craig) I know that you have to be really careful about making any kind of promise about how much you can lose on a program. But the website seems to be particularly hesitant to give any real info about possible weight loss on these pills. Based on some fine print on an ad when it first launched, it looked like an average user could expect to lose about 10 lbs in 6 months on their own or about 15 lbs in 6 months on alli. I don't know about you, but to me an extra 5 lbs isn't worth that much money and the increased risk (beyond what we already have to deal with) of accidents in public.