An unsaturated fat is a fat or fatty acid in which there is one or more double bonds between carbon atoms of the fatty acid chain. Such fat molecules are monounsaturated if each contains one double bond, and polyunsaturated if each contain more than one. In living organisms, such bonds, which are sometimes referred to as unsaturated bonds, may be either cis or trans. Cis isomers are the most common in unprocessed food stuffs.