My experience is that even with lots of water you get serious muscle fatigue starting on day 4, and major dizzy spells everytime that you sit down/stand up. Also, the body seems to go into something of a hibernation mode and want more sleep. Besides those factors, I'd say I've managed reasonably well, and I think you could continue to work a desk job just fine -- but the inability to move quickly will kill any exercise patterns you have, or, potentially, the ability to do much more than 5 minute walks. It also makes it far more difficult to get out of bed in the morning.

Interesting. I guess it depends on the kind of exercise you do.

What I noticed is that around day 7 or so, anaerobic exercise (e.g., thai boxing) becomes very demanding and hard to keep up for more than a few minutes at a time. However, it's just as easy as always to do aerobic exercise like jogging or swimming.

Never had dizzy spells or feeling of muscle fatigue (except for anaerobic exercise) - and it was also easier to get out of bed in the morning.

However, a friend of mine noted that my body goes into a super-economic mode - that I hardly lift my feet off the ground when I walk (less than an inch on average), and that my arms seem to move quite a bit less.

I wonder if the insertion of lemon juice is enough to counterbalance the dizzy spells. I recall doing long walks but not any jogging while doing longer fasts.

I'm very surprised by the lack of muscle fatigue though. I've done fasts of 4+ days 10+ times and I always get significant muscle fatigue around that point (esp. in the hamstrings).

If the lemon juice does it, it's something other than the sugars - I didn't even use a whole lemon through 21 days.

Very curious now what causes the dizzy spells. Please send me a github message or something if you ever find info. This is a long term interest of mine.