Updated November 25, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Definition: Cholesterol is a fat-like substance in the body. Most of the cholesterol in our bodies is produced in the liver, though some of it comes from the foods we eat. The body needs some cholesterol, as it is important to the body's cell membranes and to the production of certain hormones, and helps act as insulation for your nerves. Cholesterol also aids in the manufacture of bile (which is stored in the gallbladder and helps digest fats).

Too much cholesterol may cause gallstones. It can also lead to a buildup of fat in the arteries, which may cause atherosclerosis, a disease that slows or stops blood flow.

Pronunciation: koh-LESS-tur-ol