You'd get tired. They type of tired where you are just done - not exhaustion, but that combo where you just mentally and physically can't do anything. Like when you are sick and push too hard.
My LC basically turned off thee ability for my body to process sugar. If I struck to no carbs and what in ketosis, I had energy. But as soon as I snuck a cookie or two, I was bed or couch ridden for a bit. Until I got into ketosis. They boom energy again because my body would use fat, not sugar, for energy.
You'd basically feel you had the flu but without the fever and aches. Need to sit down then poof, energy gone and done.