Re: 40 day water fast
I fail to understand. If you truly mean water-only for each of those periods, I think you're describing something quite close to the average limit of human survivability, but, others, herein, I think, are claiming some very long stretches, which I assume are not within a medical setting, which - if true - would fly in the face of what I thought possible or to be recommended in attempt.
If you are greatly overweight, you might be able to survive, but there is risk of myocardial infarction.
I've never gone for longer than just over 4 days, so, even 10 days with only water (or, in my case water, coffee, and tea) seems to be beyond what makes sense for anyone, but, maybe I'm wrong. I'd urge caution.