There are four basic kinds of fasts: absolute, radical, normal, and partial. Below is a brief explanation of each as well as additional important information.
Absolute fast- No food or liquid (not even water) is consumed. Supernatural sustenance is necessary. An absolute fast is VERY, VERY RARE AND VERY, VERY DANGEROUS unless the Lord has specifically and unquestionably called you to this type of divinely protected and sustained fast.
Radical fast- Only water is consumed. A radical fast is also rare and not recommended for long periods of time unless the Lord has specifically and unquestionably called you to this type of fast.
Normal fast- No food is consumed; liquids include water, clear broths, and fruit and vegetable juices.
Partial fast- Some foods and drinks are sacrificed; for example, processed foods, sugary foods, and caffeinated beverages may be eliminated from your daily intake. A Daniel fast (see "Biblical Types of Fasts" link) is an example of a partial fast.
Those whom He calls to absolute and radical fasts (Moses, Elijah, Jesus) are sought for extreme and divine purposes. One who is radically fasting consumes only water; one who fasts an absolute fast ingests nothing - neither food nor water. We do encourage you to test the Spirit (Romans 12:2, 1 Thessalonians 5:21, 1 John 4:1) for confirmation as you sense a call to fast, especially for a radical fast. We do not recommend an absolute fast unless you are absolutely certain that the Lord is calling you to completely abstain from food and drink; biblical heroes who were called to an absolute fast were divinely anointed and supernaturally sustained for the duration of their fast. It is a rare person whom God calls to a radical fast; rarer still is the one He calls for an absolute fast.
More commonly, those convicted to fast undertake a normal fast where no solid foods are consumed, and physical sustenance is provided by broths, and fruit and vegetable juices. Others may participate in a partial fast where some foods and drinks are sacrificed (processed foods, sugary foods, and caffeinated beverages, for example).
As always, we at Trumpet and Torch recommend that you consult your physician before beginning any type of fast. We especially urge you to consult the Great Physician for His discernment and guidance. Expectant mothers, nursing mothers, children, and those with medical concerns may participate in the spirit of fasting while still receiving essential physical nourishment.