Before my first extended Water Fast of 20 days in December, I had practiced intermittent fasting on a daily basis. The schedule for me was to eat within the window of 12:00pm and 5pm, therefore leaving 19 hours without eating. I practiced this during the week for about 3 months. I also practiced shorter fasts of 24-48 hours every few weeks as well. I believe this primed my system and gave me the confidence and ability to perform a longer fast with less of the common side effects. Personally, I've also found it easier to transition to a Water Fast after about a week of an extremely low carb diet, so that you enter ketosis before even starting the fast.