You have many different types of lipids in your body including fats, oils, waxes and steroids. Your body uses fats as a supply and store of energy: a gram of fat contains more than double the amount of energy present in a gram of carbohydrate. The steroids in your body include some hormones. Other lipids make up the outer layer of all your cells, and the fatty sheaths that insulate nerve fibres. Cells use yet another type of lipid to communicate with each other.