It’s not an either or sort of thing. You don’t go to sleep one day not fat adapted and wake up the next morning fat adapted. Done deal, here’s your diploma. It’s a gradual process that takes a very long time as liver/metabolism synch with the demand for energy in cells and organs. You’re not out of synch one day and in synch the next and that’s the end of it. You might get more and more in sych over time, or not. You might reach a point where it’s ‘good enough’. Or it might fluctuate over time such that you’re more or less in synch from day to day. Just how in synch you are, how consistently or inconsistently you remain at a certain degree of in synch varies with yourself as well as between individuals.
In such a dynamic system, subjective criteria are not useful. Sure, I feel more alert and energetic today than I felt yesterday, therefore I’m fat adapted. But what happens when I feel dull and listless tomorrow? Am I no longer fat adapted? What’s going on? If @CarlKeller knew he was fat adapted when he could fast 36 hours and his energy never tapered… What if I can’t? Why can’t I?
I think most of us here realize it’s more complicated than we imagine. The variables are legion. I think it better to use whatever tools we have available to try to determine objective criteria, even if those tools are imperfect. Otherwise, don’t sweat the details. KCKO.