Let’s say you are dying of starvation. You pull one of your teeth out, causing blood to slowly seep into your mouth, which you swallow. The calories from the blood getting digested will delay the time you die of starvation, right? Or will losing blood while starving kill you faster?
If you have calories in your blood, you should leave them in there to get used instead of taking them out and back in. You wouldn’t be adding usable energy, you already had it.
You have energy stored in fat and muscle, but your body already is going to try and consume those without all that added stress of eating yourself from the outside.