No, that’s not correct. Ketone bodies are synthesized in the liver from excess acetyl-CoA, which is mainly generated through β-oxidation of fatty acids. This process, called ketogenesis, occurs in the hepatic mitochondria.

And while the liver can also produce glucose through gluconeogenesis, that pathway is distinct from ketogenesis and does not replace it. Both processes run in parallel during fasting.

gluconeogenesis maintains blood glucose for cells that require it for example active muscles and organs, while ketogenesis provides an alternative fuel, especially for the brain and resting muscles.