Over the last 10 years dieting theory and nutrition plans have become the new hot thing amongst Crossfit and weightlifting athletes. The initial rise of the Zone Diet followed closely by Paleo and now periodized, “flex dieting,” the world of food and nutrition has become as important to performance as pull-up mechanics. (For good reason). One of the more popular ideas running around is called “intermittent fasting.” The basic concept is to fast from food for a specified period of time during which you workout to encourage and aid in fat burn. Then, after the completion of the workout or given time period, an athlete eats a massive meal to aid in recovery and muscle development. The idea is that an athlete would give up food for a specific amount of time FOR THE SPECIFIC purpose of growth in their own wellness. However, the idea of fasting for a specific purpose is far from a new one.  
The Bible mentions fasting more times than it mentions prayer and yet so many have a massive misunderstanding of God’s command on our lives to fast. We often associate fasting with something super-spiritual and old fashioned YET we are so willing to miss a meal or fast from our phones for other purposes. In Matthew 6:16-18, Jesus speaks with the assumption that believers who are obedient to God’s calling on their lives are fasting:
[16] “And when you fast, do not look gloomy like the hypocrites, for they disfigure their faces that their fasting may be seen by others. Truly, I say to you, they have received their reward. [17] But when you fast, anoint your head and wash your face, [18] that your fasting may not be seen by others but by your Father who is in secret. And your Father who sees in secret will reward you.
(Matthew 6:16-18 ESV)
WHEN you fast. Not “if you fast” or “as you decide to” but “WHEN.”  
Richard Foster defines fasting as, “the voluntary denial of a normal function for the sake of intense spiritual activity.”
Martin Lloyd Jones adds that, “fasting if we conceive of it truly must not only be confined to the question of food and drink; fasting must be made to include abstinence from anything which is legitimate in and of itself for the sake of some spiritual purpose.”
Fasting, as with intermittent fasting, is the self deprivation of something in your life for a specific purpose. In the case of Biblical fasting, it is not just a voluntary abstinence from food but is a voluntary abstinence from food for the purpose of godliness. Fasting must have purpose. That purpose, as far as the Bible is concerned, is our own growth in holiness and God’s glory. 
I don’t know why we avoid this discipline. It’s found everywhere in Scripture and is a practice found prominent in every major Biblical character we read about. I think what keeps us from considering fasting often is a misunderstanding of its purpose. We don’t know why we would fast and when we do fast “because the Bible tells us to” we are just hungry for a day and gorge ourselves at midnight swearing to never do that again. I can remember participating in a youth group fast in high school for 36 hours. We were fasting as a way to aid in our prayer for those around the world who had not heard the Gospel. The youth group came together for a 36 hour retreat with regularly scheduled prayer times throughout the retreat. Having no real desire to cut myself off from food, (or to pray for the lost for that matter) I hid some ice cream and pizza in a refrigerator on the other side of the church and made regular trips as my stomach dictated. I gained nothing from the experience and thought fasting was just something “churchy” people did to make themselves seem holy or something only done in the Old Testament. Unfortunately, my high school perception of fasting still dominates much our culture today. 
Ok so fasting is in the Bible and we should do it. But why? And How?  
Before we ever make fasting a regular or even occasional piece of our lives there must be a clear understanding of its purpose. Donald Whitney has some wise words to help bring some clarity on why in the world we would ever fast. 
“Fasting must have purpose. Without purpose, specifically spiritual purpose, fasting is just a weight-loss diet. Without purpose fasting can become a self-centered experience that only leads to misery rather than sanctification.
These purposes can vary from strengthening your prayer life to seeking God’s guidance to expressing grief or seeking deliverance even expressing concern for God’s work or overcoming temptation. What fasting does not do, and will never do, is gain you the favor or a more open ear of God. Fasting is not a way to impress God and earn his acceptance. We are made acceptable to God through the work of Christ Jesus, not our work. Fasting has no eternal benefit for us until we have come to God through repentance and faith.”
We fast most often in tandem with prayer. However, fasting does not gain us some sort of special platform by which God will hear us or give us some special bonus points before God that will force Him to answer our prayers. In fact, fasting doesn’t change how God hears our prayers it changes how we vocalize them.  
How we choose to fast is simple. It does not have to be food we fast from. As Martin-Lloyd Jones said we can fast from, “anything which is legitimate in and of itself for the sake of some spiritual purpose.” What is crucial is that we fast from something for the the purpose of God’s glory and our growth in holiness and we use our time of denial to increase our prayer life and humble ourselves before the Lord. If you fast from food, consider using meal times to pray. If you fast from your cell phone, find times during the day in which you would spend on your phone to pray. Self-denial on its own does not make us more holy. It’s what we do with the empty space in our lives due to self-denial that may sanctify us. Whitney notes that our culture avoids this reality at all cost. He says, “Christians in a gluttonous, denial-less, self-indulgent society struggle to accept and to begin the practice of fasting. Few disciplines go so radically against the flesh and mainstream of culture as this one.” We are willing to miss meals or give up other objects or deny ourselves of certain things for things that we love. I know many athletes who give up time on the phone for the sake of working out. I know many adults who have missed meals because they were shopping or playing golf. “Whenever we believe another activity is at that moment more important, we will go without food fearlessly and without complaint. We need to learn that there are times when it cannot only be more important but much more rewarding to feast on God rather than food.” (Donald Whitney)
Consider adding fasting periodically to your lives. The expression alone elevates God to His rightful place above your heart’s desires.
Resources:
Celebration of Discipline: Richard Foster
Disciplines of a Godly Man: Kent Hughes
Spiritual Disciplines for the Christian Life: Donald Whitney