I am a Christian and fasting is pretty common in my church where it is used in combination with prayer. Man that sounds a lot weirder than it did in my head. Anyway fasting helps you to remember to pray for something which is really important like for example we might have a week of prayer for the NHS where everyone prays for all the different aspects of the health system. Obviously not everyone necessarily fasts and people may choose to fast for a day, or in the evenings or for the whole week if they are feeling particularly called to pray for the NHS.