Fat - Wikipedia The most common type of fat, in human diet and most living beings, is a triglyceride, an ester of the triple alcohol glycerol H(–CHOH–) 3 H and three fatty acids. The molecule of a triglyceride can be described as resulting from a condensation reaction (specifically, esterification) between each of glycerol's –OH groups and the HO– part of the carboxyl group HO(O=)C− of each fatty ...