I went into the pharmacist about these once, he explained that yeah they limit your fat intake, so if you eat too much fat in one meal it will quickly leave your body in the form of an oily discharge. However, he also told me they won't work on there own, a healthy diet is necessary, they only add to what you would already loose, for example if you worked hard all week and lost 2lbs yourself the alli would prob help you loose one more lb..... I don't think its really worth it considering the side effects, better off just sticking with the healthy diet and some exercise.