I did the blood work for diabetes because it does run in my family and I came back no diabetes, first thing I thought might be the problem.
I suspect I went into starvation mode. Thirty years ago I was much more active and physically able to exercise, now not so much due to an Gillan-Berra type illness from my past.
Sorry you are having trouble. I went through the same things you are with the culprits being steroids, diabetes, and my own stupidity. But be very careful of low carb diets as they can, at some point, start an action like a partial shutdown of body functions as those parts aren’t getting the fuel they need. I learned this first hand fro a doctor when he tried one and had to be transported back to the office during a recreational jog from exhaustion. That means muscle failure. (And the heart’s a muscle) Hope you get where you are trying to go.
rwood