Like the proverbial apples and oranges. There's no comparison between a long term fast before God and the mystical focus of bretharians. I have met several individuals who have gone on 40 day fasts (while drinking water I might add) as a way to be more receptive to the Holy Spirit. Of course these individuals returned to a normal lifestyle once their fast was over. But the important thing is the fast itself was not the central theme, quite the opposite, God was, and the fast was just a means of removing all distractions and desires.