I think if someone is an adult and is highly educated about the process, then one can fast without a doctor's supervision. Fasting can result in what can seem like scary symptoms, like dizziness, or heart palpitations, so fasting on your own is a lot of responsibility. If you want to leave all of the work up to someone else, best to go to a fasting clinic or see a fasting doctor regularly who can guide you through the process.

I do tend to cringe when I read about someone wanting to do a 30 day fast with no experience.

I personally don't think anyone should undertake a long fast straight off the bat unless there is a severe illness. I really believe it is important to gain experience slowly and see how you feel and monitor how your body reacts to certain things. Starting with 1 day, then 2, then 3, then 5, 7, etc.

I did countless short fasts ranging from 1-10 days, 1 and 2 week juice fasts (feasts), even The Master Cleanse for 2 weeks (which made me feel great despite the fact that I have read much against it that would probably make me choose something else instead), before attempting a 3 week water fast. I would have never jumped straight in without a lot of previous experience. A year after the 3 week fast, I did another one for about 3 weeks.

Anyway, fasting to me is a muscle you have to build up (unless one is severely ill and time is of the essence). It's possible to fast without a doctor's supervision just as it's possible to work out without a trainer. We all have to decide how much effort we want to put into something and how much responsibility we want to put on ourselves and how much we want to give to others. Just like some people should have a trainer, some people should have a doctor's supervision. We all have to make adult decisions for ourselves.

Of course some people are going to embark on a journey that I might otherwise see as unwise, but that is the decision of the individual. I also know some people have embarked on a fast, expecting to do maybe 7-10 days, and they feel so good, they continue on for another week or two. I wouldn't necessarily see anything wrong with that, if the person was listening to the feedback that the body was giving.

This is how building up experience to me is helpful, because you start to learn about what may or may not be a reason to break a fast. I know on my first 21-day fast, I definitely had symptoms that might have made me break it, but I had enough experience to know that I should wait it out a while before doing that.

The other issues of course that have been mentioned are that not everyone has access to a fasting doctor or clinic or can afford it, or can take the time off to do it. So fasting can be a DIY experience because there is not a good alternative available. So again building up the necessary experience for this is the key and the insurance for having a good experience overall, in my opinion.