Lipids are fats that are either absorbed from food or synthesized by the liver. Lipid metabolism refers to the processes that involve the intercourse and degradation of lipids. The types of lipids involved include: Bile salts, Cholesterols, Eicosanoids, Glycolipids, Ketone bodies, Fatty acids, Phospholipids, Sphingolipids, Steroid, Triacylglycerols (fats).