By eating excess quantity of fat or increased calories of food intake, the excess not utilized energy is converted into fat and is stored in the body responsible for weight gain. When excess fat is taken it is digested and broken down to simple compounds for absorption.
Some of the weight reductions drugs have their action on central nervous system to either suppressing the appetite or increasing the metabolism. In contrast the mode of action of Xenical is focused in the digestive system blocking 33 % of fat present in food getting absorbed.
Xenical gets attached with the Lipase Enzyme and blocks its action to digest fats in the Digestive system for breaking down of fats. This blocking activity is restricted to 33 %. In other words 33 % of the fats one is taking are not absorbed and go out of the digestive system as unabsorbed fat in the bowel. Thus 33 % of fat ingested gets out as it is without getting absorbed.