how long should a fast be
one day fast or 24-hour fast. This is the recommendation for beginners. But don't discount even shorter fasts if you've never fasted before. Sixteen hour fasts can be helpful, as can adhering to the natural nightly fast of 10-12 hours.ou would take half the number of days of the fast for each transition period, essentially doubling the number of days between start and finish. So a 10 day fast would then require 20 days of attention and commitment from you.