alli® is the only OTC drug for weight loss that is FDA approved. The unique molecular structure of alli enables it to bind to and inactivate gastrointestinal (GI) lipases, which aid in the digestion of dietary fats (triglycerides). alli binds to gastric and pancreatic lipases, blocking absorption of about 25% of consumed fat. Undigested fat is excreted from the body instead of turning into stored fat. The absorption of carbohydrates and proteins is not affected. alli is not an appetite suppressant and does not work systemically, so it will not affect the heart or nervous system and is minimally absorbed.