Xenical Chemical Structure - XENICAL acts locally to inhibit GI lipases, blocking the absorption of approximately 30% of dietary fat. XENICAL is indicated for obesity management, including weight loss and weight maintenance, when used in conjunction with a reduced-calorie diet. XENICAL is also indicated to reduce the risk of weight regain after prior weight loss. XENICAL is indicated for obese patients with an initial BMI of 30 kg/m2 or 27 kg/m2 in the presence of other risk factors, such as type 2 diabetes, hypertension and dyslipidemia.