The claim describes a basic, well-established biochemical principle: because acetyl-CoA enters the citric acid cycle where its two carbons are released as two molecules of carbon dioxide (CO2) before oxaloacetate can be withdrawn for gluconeogenesis (the net yield of the cycle is zero net carbon gain from acetyl-CoA), net synthesis of glucose from acetyl-CoA is impossible in animals. None of the retrieved papers specifically test or refute this foundational textbook principle. Therefore, it is categorized as common knowledge.