I did a 3-day fast as an experiment once. On the 3rd day in the evening, we were going to have a nice dinner. Now, I biked all over town on that 3rd day and I was feeling like utter crap/collapsing afterward. I also slept a lot during these 3 days.
Do we eat ourselves sick, or is it just those who eat too much?
90+% of us (me included) eat too much.
Not to come off as a jerk but did you do much research before you did that fast? It is quite safe to fast for a lot longer than three days, but your body is going though some weird things. The energy you use is coming from you, not just stored fat, but your muscles too will be consumed.
The fasting experts strongly suggest planning well before a fast.
- ease into it, switch to raw vegetables for a couple days before hand even (although sometimes if you ease into it too slowly it can cause a double bubble of hunger pains)
- focus on relaxation for the first couple days at least, or as much of the fast as possible... if you can be at a cottage reading, at home meditating, or if you play an instrument just lock yourself away for a couple days and play... Whatever relaxes you
- exercise is not suggested for noobs to fasting, I've only done 4 fasts or so over the years, and I wouldn't consider biking during that time, I'd maybe go for a nice walk through a forest, along a beach, etc. but nothing to really strain yourself
- ease out of the fast: your system has got used to going in slow motion, and consuming body stores of energy, fat and muscle, you don't want to shock it out of that! Have some fresh squeezed juice for lunch on the first day after the fast, and if you want to come out fairly quickly (if you're going back to work on the second day after the fast) you could have a medium sized helping of raw or steamed veggies for dinner
All this talk has me thinking about fasting this weekend! I've been sick for a couple days, so basically had nothing but thin soup, it wouldn't be a shock to my system to go to water and green tea for a couple days, although I think it is likely a bad idea for my immune system...