TEXT Xenical is not a magic pill that will melt away pounds without effort. It's most effective when paired with sustained lifestyle modifications, including balanced nutrition and regular physical activity. Assess whether you are prepared to follow a low-fat diet consistently, as consuming high-fat meals while on Xenical can lead to unpleasant gastrointestinal side effects. In addition, you will need to be vigilant about taking your medication with meals and possibly supplementing with vitamins, as Xenical can interfere with the absorption of fat-soluble vitamins like A, D, E, and K.