Active ingredient: Orlistat
Orlistat, the active ingredient in Alli, is a lipase inhibitor and works by binding to specific enzymes that break down fats (triglycerides). As a result, about 25% of the consumed fat is not absorbed and passes through the digestive system and is naturally excreted by the body. Since the calories associated with this unabsorbed fat are not used (1 gram of fat=9 calories), the number of calories that enter your system is reduced.