I am yet to figure out how long and how often. I was happy through a 20 day in the dead of winter that too, except on days 15 and 16 but that may have been that particular situation too.
I am still experimenting. So no idea. Being on a 1 meal a day schedule anyway, I am not sure what even I should change.
Thanks.
Srinath.

Are you in good health? Are you a male or a female? How old are you? What is your diet?

So there are many factors that will affect the pattern you seek. Also pain is relative. To you something will be painful and not to others and vice versa. Pain from fasting depends on how clean your body is. I fast relatively without any symptoms now after so many years of regularly fasting.

For you to figure this out, you have to try it your self. I would say do five days a month and do it again a month after, keep a diary of what you eat how you feel and then try fifteen day fast. And then there are so many variations of pattern of fasting. Some do two days every week, some do 1 day a week. Whatever you choose to do the most important part is that the period in between fasts should be 1 or 1.5 times the number of days you fast.

No pain no gain.

Happy fasting.

Archus