Orlistat is a long-acting and potent specific inhibitor of gastrointestinal tract lipase, appearing as white or white-like powder at room temperature and being insoluble in water, soluble in chloroform and easily soluble in ethanol. It can form covalent bonds with the active serine sites of the gastric lipase and the pancreatic lipase in the stomach and small intestine cavity, resulting in inactivation of the enzymes. Fat in food can’t be broken down into free fatty acids and monoacylglycerols so that the fat can’t be absorbed and utilized, thereby having reduced the body's calorie intake to control the body weight.