fat [AS, faett] , 1. a substance composed of lipids or fatty acids and occurring in various forms or consistencies ranging from oil to tallow. 2. a type of body tissue composed of cells containing stored fat (depot fat). Stored fat is usually identified as white fat, which is found in large cellular vesicles, or brown fat, which consists of lipid droplets. Stored fat contains more than twice as many calories per gram as sugars and serves as a source of body energy. In addition, stored fat helps cushion and insulate vital organs. See also adipose, obesity.
