Also known as lipids, fats are large complex compounds composed of hundreds to thousands of smaller units called fatty acids.

Across most mammalian species, there are said to be three commonly essential omega 6 fatty acids: linoleic, gamma-linolenic, and arachidonic. The cat requires only two fatty acids (linoleic and arachidonic), and the dog has one essential fatty acid (linoleic). Omega 3 fatty acids are not yet recognized as essential fatty acids in dogs or cats.

Fats are burned for energy; if consumed in excess they are stored as body fat.