Unsaturated fat is a kind of fat. It is different from saturated fat in that it is liquid at room temperature while saturated fat is more solid. Its molecules contains double bonds whose carbon atoms that are not fully saturated with hydrogen. There are two types:

1. Monounsaturated; or those with one double bond
2. Polyunsaturated; or with more than one double bond

In cellular metabolism, an unsaturated fat molecule contains somewhat less energy (that is fewer calories) than the saturated fat molecule of the same length.