Lipase is an enzyme which makes you fat. Lipase inhibitors may affect the amount of fat absorbed, yet they do not block the absorption of a particular type of fat.[1] Likewise, lipase inhibitors are not absorbed into the bloodstream. Lipase inhibitors bind to lipase enzymes in the intestine,[2] thus preventing the hydrolysis of dietary triglycerides into monoglycerides and fatty acids.[3] This then reduces the absorption of dietary fat.[2] Lipase inhibitors covalently bond to the active serine site on lipases. This covalent bond is strong, meaning the lipase inhibitor tends to remain attached to the lipase.[4] Studies have shown that lipase inhibitors work optimally when 40% of an individual’s daily caloric intake is obtained from fat.[1][clarification needed] Orlistat tends to block absorption of 30% of total fat intake from a meal, as orlistat passes out of the digestive tract more rapidly than fat does.[2]