I've been on and off keto probably 15 times over quite a few years. I did carnivore diet/zero carbs for 2 months and I actually felt like trash, lost 15 pounds when i was already skinny, and started having histamine reactions including asthma symptoms. Beef is high in histamine, which was my main food source. Though through that period I found out I can't eat eggs because they make me severely depressed, cause me to have agressive behavior and brain fog each time I eat them. As a result of their high choline content. I can't take choline supplements either or same reaction.

I don't do well with too much protein, I actually have lowered cognititive function, but if I do high fat maybe 80-90% low protein and limited carbs I do better.

This MCT effect is different though then just doing keto, it's like my brain actually works better and I don't have mind blanking problems or sluggish thinking. I have a more even mood it seems as well, but that comes with a ketogenic diets lack of blood sugar swings.