Fasting is something sacred between God and man. It is not something to be displayed to the world but is actually a private matter.  It is not about an external display of righteousness, but something that is done in secret, in the hidden place.  Jesus teaches us how to fast.

“When you fast, do not look somber as the hypocrites do, for they disfigure their faces to show others they are fasting. Truly I tell you, they have received their reward in full. But when you fast, put oil on your head and wash your face,  so that it will not be obvious to others that you are fasting, but only to your Father, who is unseen; and your Father, who sees what is done in secret, will reward you” (Mt 5:16-18). 

Here are the instructions:

• Do not look somber
• Shower up, look extra clean and sharp
• Make your fasting not obvious in the slightest
• Make it about you and Your Father who is unseen

In essence, no one should know you are fasting.  This is something holy and private between you and the Lord.