The fatty acids are broken down starting at the carboxyl end. The enzyme acts on the carbon atom third from the end to oxidize it to a carboxyl group while splitting off the other two carbon atoms as acetate. The sketch shows a fatty acid with ten carbon atoms. It is oxidized to an eight-carbon fatty acid and acetic acid. The same enzyme goes to work on this fatty acid to make one with two less carbon atom plus another acetate.
Most fatty acids have an even number of carbon atoms and are broken down to acetate.
Acetate is also formed from the breakdown of sugars, and one common path can serve for both fats and sugars from acetate onward.