I was watching my fiance run and someone died literally right in front of me at the Brooklyn half-marathon in the fall (he was a young guy - I'd say late 20s). He collapsed right at the finish line and they couldn't revive him. The crazy thing is there was no mention of it after the race or anywhere, I tried googling to find out more info. but nothing. The only info. I found was on /r/running people where people who were also in attendance were talking about it. Marathons just seem so unnatural to me.
From the "Those who don't learn History are doomed to repeat it" department: the whole reason people "run a Marathon" is because of the legend of a Soldier, Pheidippides, running from Marathon to Athens and dying after announcing victory in battle.
If people are aware of this basic information and still are stupid enough to run without any preparation, I'd say they would be candidates for the Darwin Awards.
No, I am saying that the people who "run past their breaking point just for giggles" (to use parent's term) are acting so carelessly that I don't care if something fatal happens to them.
Call it "self experimentation" all you want, but the OP running a 50k while on 4-day fast is plain stupid. It would be by his own damn doing if he died or done any serious harm to his body.
I think you have to think about how those people died. Heat exhaustion? An underlying heart condition? I don't think they died of not having enough nutrients, or not eating soon enough before running.
Sometimes stroke or similar, caused by incorrect hydration by just drinking lots of plain/plain-ish water which leave various useful things in your body too diluted to be useful. Sometimes an exacerbating factor in heat stroke, so not diagnosed as the heat stroke is seen as the only problem and other causes of heat stroke are assumed. See https://en.wikipedia.org/wiki/Water_intoxication