You've got to get past about 36 hours before your body / brain stop acting so "berserk." After that, you stop being hungry and you can look at food with relative equanimity.
I fast pretty regularly for a day here and there. Used to do it every 4 days but fell off the bandwagon. Have done plenty of 2 day fasts too.
This is one of the silliest things said about fasting - and that is saying a lot.
Never had all this energy either.
I didn't have nightmares but I do remember that my dreams during the fast were incredibly vivid. I never imagined such dreams were possible and it's one of the things I miss most since ending the fast.
IMO, artificially supplementing those during the fast will throw off your body's sensors if you will of knowing when something is abnormal.
This morning, I woke up about an hour earlier than usual with a great feeling of energy and focus. No real hunger. I'm going to push it a little further as long as I feel good. Thanks.
I've heard it said that what most people in the developed world describe as "hunger" is really just appetite. A different phenomenon, and an uncomfortable one, but separate from true hunger, which tends to set in after a few weeks, and is more like a psychological impulse to acquire food by any possible means, including violence.
I feel a bit dizzy at around 20 hour mark, past this I feel absolutely fine, can do interval training like always and have no hunger at all. On 3rd day I can start noticing some physical limitations, like when I tested how many hills can I climb on a MTB until I hit the wall hard (shaking muscles, mild spasms etc.), and the time I can spend doing athletic level of activity decreases every day (like 6 hours in the beginning to 1 hour after two weeks).
Did you happen to get measures of your body fat pct before and after?
Another method I've done is a net-zero where I eat say 600 calories and run a few miles so there's not as much muscle loss.
I like the net-zero approach. Do you make those 600 cals primarily from protein? BTW, it's about 100-120 cals/mile typically. (I'm a runner and use 100 cals/mile since the math is easier and close enough.)
Also, in the first 48 hours of the fast I did a rather extensive physical workout program which is meant to bring your body into a keto state much earlier than it would otherwise.
At the end of the day I feel like I got to know my own body on a whole new level. I didn't do it with the intention of losing the weight, but of course it was a welcome addition to all the other benefits I took away from this experience. In a year or two I plan on doing another one for 40 days.
For two years prior to this fast I suffered from mild pain in my left knee which made it very difficult to get up from the floor or run for more than a few minutes. Two weeks into the fast, that knee began to hurt like crazy. By day 16 I was unable to bend it. But that was somewhat expected. Many peopl who undertake a prolonged fast report what is referred to as a "healing crisis"- when the body is in a state of self healing during which pre-existing symptoms flare up as the body works to get rid of them.
Who knows what I had in my knee. Gout, pre arthritis, some nasty build up of fluids... Either way, it's all gone. After 3 days of being unable to stand or even slightly bend that knee - it all disappeared. I woke up on day 19 and it was as if I had a new knee. All symptoms are gone since then and I have resumed my hiking and biking activities and am glad I let it heal itself.
And to answer your other question, at 5'9 I weighted 182 at the beginning of the fast and 147 on day 23. I wasn't terribly overweight, and now at my ideal weight.
And day 21 is far from being at the point of true starvation. That doesn't normally happen until at least day 45.
My other concern is that I run 50+ miles/week and I assume that would be impossible while fasting. I'd also be bummed about loss of muscle mass.