I've never heard that but could be true I guess.
I haven't done a true fast before though I did one similar to the yearly muslim(?) fast of not eating during the day and only at night. despite obviously being famished at night I did feel a cleansing affect from it and would like at some point to do it again though you need to have plenty of rest and not be going to work or such.

A doctor told me a few years ago a theory about many years ago when humans still lived in small vilages as such (some still do) and lived more by the seasons as you said Abandit. At this time we had a natural fasting cycle due to times of less food so the body tended to be cleaned more naturally but now we have high quality food year round and don't give ourselves that opportunity.So we tend to clog our bodies with to many toxin etc, **** I'm scaring myself now think I'll leave it there.