I have fasted for 2 weeks. I think that for a young healthy human one week will rarely cause problems. But after the first week I was permanently cold on the inside (I am a person that never wears long sleeves or jacket even if it is -10 Celsius outside) so I said - enough for now.

Medical supervision - whatever makes you feel best - if you will be calmer with having someone check you daily go for it.

Fasting is something that is individual - I have had involuntarily fast lasting 72-96 hours while playing diablo. But I have friends that cannot get a single afternoon without food - they fainted.

A good test is 18 hour inteminent fast, then cut your teeth with 32 hour one (you eat dinner on Monday before going to bed and next meal is Wednesday breakfast) - if you feel anything than hunger and some psychological discomfort - maybe it is not for you.

> How long would you be comfortable fasting for without medical supervision?

One week if you don't have any major health issues.

Not even a day if you're suffering from some serious condition.

Plan for less physical activity than usual, but do not become a vegetable. Take some short walks, do some small work with your hands. Meditation is great during this time, but you have to be somewhat accustomed to it.

Restart eating step by step. Begin with some fruit juice or clear soup. Then graduate to very soft, almost overcooked rice or something like that. A vegetarian diet for the first few days is beneficial. The longer you're fasting, the more cautious you have to be with restarting your diet.