Generic Alli (Orlistat) is used for managing obesity in overweight adults. Generic Alli (Orlistat) is also used to reduce the risk of weight regain after previous weight loss. Generic Alli (Orlistat) is used along with a reduced-calorie and low-fat diet. Generic Alli is a gastrointestinal lipase inhibitor. Generic Alli (Orlistat) works by blocking the digestion of fats from the diet. Generic Alli (Orlistat) blocks some of the fat that you eat, keeping it from being absorbed by your body. Generic Alli (Orlistat) is used together with a reduced-calorie diet and weight maintenance to treat obesity in people with certain risk factors (such as diabetes, high blood pressure, and high cholesterol or triglycerides).