What is "unsaturated fat"

n. A fat or oil, from either animal or vegetable sources, containing a high proportion of unsaturated fatty acids; will typically be liquid at room temperature; a diet high in unsaturated rather than saturated fats is thought to contribute to lower levels of cholesterol in the blood.

An unsaturated fat is a fat or fatty acid in which there is at least one double bond within the fatty acid chain. A fatty acid chain is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond.

Where double bonds are formed, hydrogen atoms are subtracted from the carbon chain. Thus, a saturated fat has no double bonds, has the maximum number of hydrogens bonded to the carbons, and therefore is "saturated" with hydrogen atoms. In cellular metabolism, unsaturated fat molecules contain somewhat less energy (i.e., fewer calories) than an equivalent amount of saturated fat. The greater the degree of unsaturation in a fatty acid (i.e., the more double bonds in the fatty acid) the more vulnerable it is to lipid peroxidation ( rancidity). Antioxidants can protect unsaturated fat from lipid peroxidation.