Orlistat is a prescription-only weight loss medication that contains the active ingredient of the same name. It works by blocking the enzymes responsible for absorbing the fat you eat and instead removes it from your body as stool waste. Orlistat is available in the form of an oral pill. When taken alongside a healthy calorie-controlled diet, it is an effective weight loss medication. Research has found that orlistat can help 37% of people lose 5% of their body weight after 12 weeks of treatment.