Xenical - Version 1 Xenical is used to help obese people who fit certain weight and height requirements lose weight and maintain weight loss. Xenical works in your intestines, where it blocks some of the fat you eat from being absorbed. This undigested fat is then eliminated in your bowel movements. Use Xenical together with a reduced-calorie diet. The weight management effects of Xenical continue only as long as you are taking it.