When insulin levels are low, the liver begins to oxidize fat. The liver oxidizes fat by an incomplete process that yields ketone bodies. The incomplete oxidation of fatty acids by the liver yields some ATP. Ketone bodies can be further oxidized to yield ATP. Is the net ATP produced from one gram (or mole or carbon) of fatty acids the same whether the fatty acid is oxidized directly by beta oxidation versus whether it is partially oxidized by the liver and then the resulting ketone bodies are oxidized?
Stearic acid would be a good standard FA to compare oxidation through ketosis versus direct beta oxidation.