Did you find that you got light-headed when you stood up too fast after 14 or so days? I fasted for 25 days (water) and found that I would get a little bit light-headed if I stood up from a seated position too fast. I also found that I would have these weird nightmares where i was eating a ton of food and would wake up thinking I had ruined my fast...very bizarre. I have never talked personally to anyone that had also fasted longer than a week, so I was interested if your experiences mirrored mine and if you found any way to reduce that light-headed seeing stars kind of feeling when you stood up. Other than that, I'd say I didn't notice many other issues except for maybe a quicker onset of fatigue if I was climbing a flight of stairs or something.

Not so much, no. I did attempt to paint a wall around day 16 I think and didn't feel comfortable looking up while standing on the ladder so decided to put it off until I ended the fast. Other than that I felt as normal as can be during the entire fast, although I couldn't get myself to stay up very late and so my evenings would end around 9pm.

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.

Can you please explain what you ate or drank over that 25 day period?

Not the OP, but when I fasted I only drank water, usually distilled. You don't eat anything, hence the term water fasting. I should mention that I personally got weekly blood tests to keep track of the vitals (especially potassium levels) and this is something you definitely should do especially if it's your first prolonged fast.

Interesting. Why did you stick to distilled water, as opposed to having some (non-caloric) electrolytes?

Most people do not reach a point where their electrolyte levels are dangerously low when undertaking a prolonged fast of up to 40-45 days. Low levels of electrolytes are an indication that your body is unable to continue in a fasting state for one of several reasons, and it must be stopped.

IMO, artificially supplementing those during the fast will throw off your body's sensors if you will of knowing when something is abnormal.

Only water. Tap water or bottled water, not distilled for me. Other than that I ate nothing, no vitamins or electrolytes or anything, just water.

I find this remarkable. Not saying that I absolutely don't believe you, but I'm struggling. This would seem more like starvation than fasting, and sounds potentially very dangerous. For a little context: http://www.scientificamerican.com/article/how-long-can-a-per...

Sorry- but you mean that you didn't eat anything at all for 23 days? And you felt energized?

Correct. I did not consume anything but water for those 23 days. And yes, past day four I felt more energized than at any time in the last 10 years or so. I know it sounds counter intuitive, but I guess it's one of those things you have to try to feel for yourself :) Even the people around me that knew I was fasting were surprised to see the progression and how much more energetic I seemed. Anecdotally, I did feel at least five years younger at the end of the fast - physically and mentally.

It's not really that counter-intuitive. Presuming humans evolved to cope in situations where food was sometimes very scarce, and had to be acquired through hunting and gathering, likely in competition with other individuals and groups, then being listless and incapable for months as our body's stores of fat and muscle drained away would not be helpful. Far better for the body to expend its store in a few weeks of energetic activity spent searching for replacement food supplies.

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.

@crusso, haha I only heard about this show when my friend suggested that I go ahead and apply to participate. It does take some mental effort to cruise through a prolonged fast. It's especially hard in our society where so much is centered around food. It was inconvenient at times to be the one who doesn't eat in social functions and such, but you get over it. The key is not to talk about it and have to explain to people why you're not picking up a beer at the BBQ. Also this wasn't my first prolonged fast, and I know from experience that it does get easier the more you condition your body to rest and take a break from constantly digesting.

Inspired by this thread and your post, I decided yesterday to try at least a 24 hour fast. After a breakfast shake yesterday, I played tennis and went about my normal activities. I eat a fairly ketogenic diet, so the hunger wasn't too distracting, although I felt very laid back in the evening.

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.

Glad to hear! Feel free to reach out via email if you have any questions or interested in several resources that will go into great detail with regards to prolonged water fasting.

None of the people I've seen so far on Naked and Afraid seemed "energized" after not eating for days.

I think they are often also dehydrated, full of bug bites, uncomfortable, lacking sleep, and stressed out, so not sure how comparable it would be to fasting in the 1st world.

How much time in between prolonged fastings do you believe is healthy to do it? I'm pretty interested in finding a good time eating - time fasting intervals where I could take advantage of the energy given by the fasting time and the reload of food in our bodies? Hmmm a guess for me (I don't know about the topic) would be a 10 days each 2 months, maybe? You did some kind of exercise or some activity that required big efforts?

Take into account that eg day-on day-off fasting would also have an effect on your body, not just the long fasts.

I have a similar experience when fasting!I feel a bit more energised and definitely have a clearer mind.

I went thru the same on a 14 day fast. More energy after about day 3, clearer thinking etc.

Add a bit of salt/minerals to your water or you risk lack of electrolytes, but you probably know.

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).

How much weight did you lose over this period? With a TDEE of 2400 cal/day, you'd theoretically lose almost 5 lbs/week, though I imagine your metabolism slows down. Still, I'd guess you lost 10-15 lbs?

Did you happen to get measures of your body fat pct before and after?

Not OP, but in 25 days of water fasting I lost 30 pounds. 196 -> 166. I gained about 15 lbs back within a week after I stopped fasting, then settled in the mid 180s. I did not measure body fat percentages, but I could tell I was losing just as much muscle mass as fat by the second week.

No OP also... I was about 1-1.5 lbs a day once you get past the first 3 days.

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.

It's generally accepted that a deficit of 3500 calories causes 1 lb of weight loss. And most men burn around 2000-2400 calories day. So 1 lb (much less 1.5) surprises me. I wonder why the math doesn't quite add up.

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.)

I lost 35 pounds. I didn't measure anything else, and since ending the fast 2 months ago I regained about 5 pounds. For several weeks following the fast I only ate fruits and veggies which is why I think the weight gain has been so little compared to those who fast and then resume their old diet fairly quickly.

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.

Thanks for the info. I'm interested in fasting just because I like to do these sorts of experiments. I fast once a year for 24 hours and I'm pretty hungry by the end... so I'm not sure I have the resolve to go through the hunger pangs much longer than that. How long do those last?

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.

Is this safe? How do you know what your limits are? I thought around 21 days you were at the point of starvation? What about your weight? How over weight are you (if you don't mind me asking)? I'm assuming someone with a normal BMI couldn't do something like this for so long???

Just about anyone can do it safely, with the exception of people with very specific health situations. Even very skinny people who need to but cannot gain weight seem to reverse that trend following a prolonged fast. The body is very smart in turning a prolonged fast into a series of corrective actions needed to maintain its own well being.

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.