“Whenever you fast, do not put on a gloomy face as the hypocrites [do,] for they neglect their appearance so that they will be noticed by men when they are fasting. Truly I say to you, they have their reward in full. But you, when you fast, anoint your head and wash your face so that your fasting will not be noticed by men, but by your Father who is in secret; and your Father who sees [what is done] in secret will reward you.”
Matthew 6:16-18
When you fast, take measures to be certain it is not obvious to others.
Our private works of humility and worship in the service of, and communion with, the one true God should remain private. If we are sincere in preparing our hearts and bodies to be receptive to the leading of God, we must maintain that intimacy.
When our inner convictions become just an outward show, we have denied ourselves and create a mockery of God. Self-adulation and false humility demonstrate a shallow understanding of our spiritual condition for the simple purpose of bettering ourselves in the eyes of others.
Denying body and soul is a personal discipline that is meant to take our eyes off of ourselves and our own needs. Making a display of it contradicts everything it is intended to accomplish.
However, maintaining a vital and dynamic intimacy with God through our heart understanding working in concert with our actions provides great personal reward. This is an unseen way in which we are strengthened to visibly serve others effectively in his name.
The Core of the Bible 