The FDA decided yesterday to sell Xenical "over the counter." This drug, now available only by prescription, blocks about 25% of the fat in your diet from being absorbed by your digestive tract. Folks often do actually lose weight with it. Unfortunately, that grease has to go somewhere. An unpleasant side-effect is often that all that oily grease departs the body via "anal leakage."
I guess as long as you carry a couple extra pairs of drawers with you at all times, its all good.