>>10
>ケトン体にまでなれば体脂肪に戻らない。

Ketone bodies have been regarded as an energy source that is mainly produced in the liver, and exported to extrahepatic tissues.
However, ketone bodies have also been suggested to be used during the lipogenesis...
https://www.ncbi.nlm.nih.gov/pubmed/22985732

...cytoplasmic de novo lipogenesis (DNL) and cholesterol synthesis are nonoxidative metabolic fates of ketone bodies.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3625904/figure/F1/