A person who isn’t fat adapted just sitting on the couch on a regular day will essentially burn zero fat. In a starvation scenario they would, yes. But people who aren’t fat adapted struggle terribly in starvation because their bodies are not good at converting fat to energy.

I’ve been watching that show I Shouldn’t be Alive a lot and most episodes the people who survived go many days or sometimes multiple weeks without food. None of them are fat adapted so they get very weak quickly and struggle to do that fat to glucose/glycogen conversion efficiently.

Properly fat adapted people can fast easily for many days with no energy issues. The difference is poor fat adaption vs proper fat adaptation.

It’s like a 2% efficiency vs 99%.