I am aware of the Lord teaching us to pray, detailing how and how not it should be done, but the only thing he said about fasting was
"Moreover when ye fast, be not, as the hypocrites, of a sad countenance: for they disfigure their faces, that they may appear unto men to fast. Verily I say unto you, They have their reward. But thou, when thou fastest, anoint thine head, and wash thy face; " (Matthew 6:16-17).
I do not recall where in the bible but I know faithful servants of God like David, Esther, Isaiah, Barnabas and Simeon fasted. We are even admonished to fast for spiritual strength.
"Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency." (1 Corinthians 7:5).
How do christians carry out this exercise when food is very important for strength in the physical?
"If ye love me, keep my commandments. " (John 14:15). How do Christians keep this very commandment?
Please if anyone could help me put this question in a better way to avoid closure, edits are welcomed [Expecting @RiverC's answer among the responses as he inspired me to reask better.]