Various forms of fasting have become fashionable for health-related reasons. I cannot comment on those medical implications, nor do I offer specific advice on how to fast.
But the bible clearly places a special emphasis on fasting for spiritual purposes. In Matthew 17:20 (KJV), Jesus speaks of the power of faith,
If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you.
But he adds a rejoinder in the following verse (Matthew, 17:21, KJV),
Howbeit this kind goeth not out but by prayer and fasting.
The practice of fasting often gains renewed attention during Lent. And I must confess that I do not understand the full implications of fasting. But if Jesus attests to its importance, then it's something we can't ignore.
Of course, hunger is a very base, lower-level urge, and one that is intricately linked to our very survival. So perhaps the process of confronting that sensation, even for a short period of time, forces us to refocus on spiritual concerns.
Whatever the importance and consequences of fasting might be, the bible does not appear to prescribe a "correct" way in which to go about it, suggesting that the specific parameters are probably up to us. Perhaps a small-scale fast can enhance our prayer lives.
