If you have never fasted before, I applaud your present interest! Fasting has been a major emphasis in the lives of many of the great spiritual leaders throughout history. John Wesley, the founder of the Methodist denomination, fasted every Wednesday and Friday and required all of his clergy to do the same. Effective ministers of God from the apostle Paul to Martin Luther to John Calvin made it a continual part of their walks with God.
None of those men had a "formula fast" that was the only "right" way. Fasting is about the condition of the heart, not the number of days. Each time that I have fasted for forty days, it was because I felt impressed by God to do so.
So, start slowly. Fast for one meal a day, or one day a week, or one week a month. Build up your spiritual muscles so that you will be prepared in a period of several months to fast for an extended 40 day period.
The Bible Recounts Primarily Two Types of Fasts
A partial fast is described in the book of Daniel. Although the water fast seemed to be the custom of the prophet, there was a three-week period in which he only abstained from "delicacies," meat, and wine (Daniel 10:3).
The two primary types mentioned in the Bible are the "absolute" and "supernatural absolute" fasts. These are total fasts-no food (solid or liquid) and no water. Paul went on an absolute fast for three days following his encounter with Jesus on the road to Damascus (Acts 9:9). Moses and Elijah engaged in what must be considered a supernatural absolute fast of forty days (Deuteronomy 9:9; I Kings 19:8).
So, I strongly advice you to drink plenty of liquids. Obviously, if God leads you to undertake an absolute fast, you should obey. If so, be certain, without doubt, that God is leading you.
Water-only fasts that last for more than several days need to be undertaken with complete rest and under medical supervision because of the extreme danger of over-toxification, breakdown of vital body tissues, and loss of electrolytes.
I personally recommend and practice water and juice fasting, especially if you are going to fast for an extended period of time. This type of fast will provide you with more energy than absolute or water-only fasts and still lead you into the humbling experience of denying your desire for solid food that you can chew.
When it comes to making your final decision about what type of fast is right for you, the best advise I can give you is to follow the leading of the Holy Spirit. He will guide your heart and mind as to what is best for you. Remember, the most important consideration in fasting is your motive. Why are you fasting? To seek something personally from God's hand or to seek His face in worship, praise and thanksgiving?