Unsaturated lipids are a type of fat. They are one of several varieties of fats found naturally -- and they are one of the healthier kinds of dietary fats.
Lipids are a group of molecules that include fats, oils, waxes and steroids like cholesterol. They are all hydrophobic, which means they repel water, and are all made of the elements carbon, oxygen and hydrogen. A typical lipid -- a fat in this case -- is composed of a glycerol, which is a type of three carbon alcohol and three fatty acid groups joined together.
What Makes a Lipid Unsaturated
Lipids are considered either saturated or unsaturated by the number of hydrogen atoms bound to the fatty acids and the number of double chemical bonds between the carbon atoms in the fatty acids. Saturated lipids have only single chemical bonds between the carbon atoms in the fatty acids, while unsaturated lipids have one or more double chemical bonds between the carbon atoms in the fatty acids. Monounsaturated lipids contain only one double chemical bond between the carbons in the fatty acids. Polyunsaturated lipids contain two or more double chemical bonds between the carbons in the fatty acids.
Saturated versus Unsaturated Lipids
Saturated lipids are typically found in animal products or come from animal sources. They are solid at room temperature because the single chemical bonds make the fatty acid chains straight and allow them to pack together tightly. Examples of saturated lipids include butter and lard.
Unsaturated lipids are typically found in plant products or come from plant sources like seeds or nuts. They are liquid at room temperature because the double chemical bonds "kink" or "bend" the fatty acid chains, preventing them from packing tightly together. Olive oil, sesame oil and avocados are examples of unsaturated lipids.