I was eating up to 6k calories a day, mostly from fat- I was VLC/ZC for ~18mos. I was literally drinking butter and other fats. Bear in mind, I do no "cardio" type things- just an active lifestyle and lifting weights(low reps). I lost 20+ pounds of muscle in ketosis. My mood was the real tell- the instant I started eating carbs, my mood skyrocketed, and cutting carbs out drops it within days.How do you know that increasing your carbs made you feel better mood and energy wise because ketosis was "not working" and not because you just needed more calories to fuel your intense level of physical training? It's difficult to get enough calories if you are lean and working out strenuously without adding some carb unless you are gong to eat 24 oz steaks covered in butter for every meal.
Sure- ketosis is good for some, and not for other, and many people fall in between. However, we also know which groups tend to do better on each. If an 19 yo athelete feels terrible in ketosis, I'm going to tell them to eat some primal carbs. If someone is in ketosis bc they have epilespy, then they need to stay in it and figure it out. In between, it's more of a discussion.I totally agree that lean, very active individuals with healthy metabolisms often do better with adding carbs. But that doesn't mean that ketosis is necessarily harmful to everyone or anyone. I know you (AP) didn't say it was but some of the carb pushers have been lately.
I do understand why people who had experience like mine are anti-ketosis, though. If I had been more prone to depression, that mood drop could have caused real problems(we're talking going from a 8 to a 4 on a 10 point scale), and in a certain cases, that insulin sensitivity could have caused issues, too. If I was driving, and reached down to grab my Zevia, and got my passengers coke instead, that swig would be bad. A contrived situation, yes, but there are risks for some.
FWIW, I lost significant fat when I re-introduced carbs.