Having done a >20-day fast myself, multiple times, knowing a few others who have, researching the medical evidence AND discussing this with more than one local doctor, I can confidently say:
That's funny, because I've talked with doctors who oversee medically-managed weight loss programs professionally, and they made it very clear that even just doing 960Cal/day for 3+ days warranted medical supervision. This is also why stuff like Optifast requires a prescription, because it's not safe to do this kind of thing without oversight.
The fact that you've done it really has no bearing on whether it's actually healthy, and I'm going to go ahead and assume that the doctors you spoke to said the equivalent of "it won't kill you but I don't recommend it".
Well, the doctors you asked had a vested interest, they are unlikely to say “we are mostly useless”, so I can just as easily discard that. See how easy it is to maintain one’s belief without evidence?
There is actually a lot of evidence saying anything up to about 40 days on water is fine for a healthy person, although beyond 50 days there is rapid and irreversible damage.
There are whole populations who used to live on 800kcal/days for years.
And for the record, my family doctor’s reply was “just make sure you start eating if you feel any ill effects, don’t go more than a month” - when I came to see him after about a week inquiring if my loss of appetite was something I should be worried about (because thinking and looking at food made me NOT want it, but I was feeling perfect - even better than perfect).
From your response you are likely uninterested, but reading the work of Valter Longo on fasting would probably enrich you.
Also, there’s a huge difference between reducing intake (to e.g. 900 of 500 kcal) which leaves most people hungry and irritated, and going down to essentially zero, which - past the 50 hour mark or so - does not. The doctors you consulted likely have no experience at all with the latter regime in which the body functions completely differently, and which seems like a natural “can’t find food right now” mode.
> Well, the doctors you asked had a vested interest, they are unlikely to say “we are mostly useless”, so I can just as easily discard that. See how easy it is to maintain one’s belief without evidence?
No, the doctor does not have a vested interest in lying to me. They're HMO doctors, this is but one facet of their job, and they're doing it because it needs medical oversight. Hell, the program itself was offered effectively at cost (it's in the HMO's interest to have healthy patients, so they charge just enough for the program to cover their expenses rather than treating it as a profit center).
In a perfectly healthy person, extended fasting is probably fine. Medical supervision isn't because it's particularly dangerous for perfectly healthy people, but because nobody is perfectly healthy and complications can arise with pre-existing undiagnosed conditions.
