I feel lethargic after eating. I find it hard to concentrate when hungry. I'm only productive in those 1-2 hours between the brain fog wearing off and the next hunger wave coming on.

I tried the meat diet for a few days (yes, I know that's too short! I couldn't get through the "keto flu") and I was blown away by how stable my mood and energy level was after having steak for breakfast. I wouldn't get hungry at all for the next 8-10 hours.