Fatty acids are composed of a hydrocarbon (acyl) chain with a methyl and carboxyl group at either end. Most fatty acids have an even number of carbon atoms that are arranged in a straight chain. The majority of dietary fatty acids range in chain length from 4 to 22 carbons. Fatty acids with 16 and 18 carbons comprise the fatty acids with 16 and 18 carbons comprise the bulk of fatty acids in both the diet and the human body.