How does Xenical work Orlistat, the main active ingredient in Xenical works in your digestive system to block about one-third of the fat in the food you eat from being digested. Enzymes called lipases exist in your digestive system and help break down fat. Xenical binds with lipases to prevent them from breaking down fat you have eaten. The undigested fat cannot be absorbed and is eliminated by your body. Can I take Xenical? Xenical is only suitable for individuals with a body mass index (BMI) of 30kg/m² or greater who have had at least 3 months of managed care which includes diet, exercise and behaviour modification who failed to adequately reduce weight. Treatment can be considered for individuals with a BMI over 28kg/m² if certain risk factors such as high blood pressure, high cholesterol, heart disease or diabetes are present. How to Take Xenical? The usual dose of Xenical is one 120 mg capsule taken with each of the three main meals per day. It can be taken immediately before, during a meal or up to one hour after a meal. The capsule should be swallowed with water. Xenical should be taken with a well-balanced, calorie controlled diet that is rich in fruit and vegetables and contains an average of 30 % of the calories from fat. Your daily intake of fat, carbohydrate and protein should be distributed over three meals. This means you will usually take one capsule at breakfast time, one capsule at lunch time and one capsule at dinner time. To gain optimal benefit, avoid the intake of food containing fat between meals, such as biscuits, chocolate and savoury snacks. Xenical only works in the presence of dietary fat. Therefore, if you miss a main meal or if you have a meal containing no fat, Xenical need not be taken. Tell your doctor if, for any reason, you have not taken your medicine exactly as prescribed. Otherwise, your doctor may think that it was not effective or well tolerated and may change your treatment unnecessarily. Your doctor will discontinue the treatment with Xenical after 12 weeks if you have not lost at least 5 % of your body weight as measured at the start of treatment with Xenical.