Cats are unique among mammals with respect to metabolism of fatty acids. Except for some ruminants, all other mammals, including cats, are able to synthesize nonessential saturated and monounsaturated fatty acids de novo from glucose or amino acids via a common precursor, acetyl CoA. The products of this synthesis are 16- and 18-carbon saturated fatty acids that can subsequently be desaturated to monounsaturated fatty acids of the n-7 and n-9 fatty acid families (e.g. 16:1n7 and 18:1n-9). These acids are the result of the introduction of a single double bond between carbons delta-9 and delta-10 of the respective saturated acids. Enzymes regulating these reactions are active when high-carbohydrate, low-fat diets are fed but have low activity when high-fat diets are fed. Consequentially, animals fed relatively high-fat diets will only synthesize limited amounts of the needed fatty acids. Instead, they directly use the dietary supply of fatty acids.