I was at the gym last week and I struck up a conversation with another member who at first was inquiring about my tattoo. He surmised that I was a Christian, basing this on the fact my tattoo has a Christian theme. He was a Christian too and then the topic of Lent came up. To cut a long story short he said that he respects Catholics for making genuine acts of self-denial during this time but stopped short of agreeing with self-denial (i.e. fasting) because he believed it was un-biblical and that the "suffering" was in vain since Christ has undergone the suffering for us. While the latter is correct to an extent the statement was not congruent with what Catholics believe and what the Church teaches on fasting, but I had to first address the assertion that fasting was "un-biblical".
Where to begin? Well let's start with Christ fasting himself. To prepare himself for his ministry, we know that - as it says in scripture - that Christ went out into the wilderness for 40 days and 40 nights without food, fighting temptation and the devil (bolded for emphasis):
And Jesus, full of the Holy Spirit, returned from the Jordan, and was led by the Spirit for forty days in the wilderness, tempted by the devil. And he ate nothing in those days; and when they were ended, he was hungry. The devil said to him, "If you are the Son of God, command this stone to become bread." And Jesus answered him, "It is written, `Man shall not live by bread alone.'" And the devil took him up, and showed him all the kingdoms of the world in a moment of time, and said to him, "To you I will give all this authority and their glory; for it has been delivered to me, and I give it to whom I will. If you, then, will worship me, it shall all be yours." And Jesus answered him, "It is written, `You shall worship the Lord your God, and him only shall you serve.'" And he took him to Jerusalem, and set him on the pinnacle of the temple, and said to him, "If you are the Son of God, throw yourself down from here; for it is written, `He will give his angels charge of you, to guard you,' and `On their hands they will bear you up, lest you strike your foot against a stone.'" And Jesus answered him, "It is said, `You shall not tempt the Lord your God.'" And when the devil had ended every temptation, he departed from him until an opportune time. - Luke 4:1-13So let's put this in perspective: Jesus, the son of God, himself fasted. When Pope John Paul II was alive I remember reading an article that said the Holy Father attended Confession once a week. I remember thinking to myself after reading that, "If the pope goes to Confession once a week then I should be going hourly!" As Christians we should apply the same principle to fasting: if Christ himself fasted, then we too should fast, which brings me to this little doozie here (bolded for emphasis):
"'And when you fast, do not look dismal, like the hypocrites, for they disfigure their faces that their fasting may be seen by men. Truly, I say to you, they have received their reward. But when you fast, anoint your head and wash your face, that your fasting may not be seen by men but by your Father who is in secret; and your Father who sees in secret will reward you.'" - Matthew 6:16-18
Note the use of the conjunction "when" in these passages. There is no "if". The conjunction is definitive, "when" implies that Christ is in fact exhorting his followers to fast but - as the passage suggests - to do so without hypocrisy, but rather to do so joyfully and without "promoting" the fact that you're fasting.
So is fasting un-biblical? It certainly doesn't look that way. My hunch is that some fundamentalists reject fasting because it appears to be a very "Catholic thing", and in their books anything Catholic is bad. In short: if Christ himself fasted and if he's exhorting the practice, then we should as followers of Christ be heeding those words and listening to his instruction, for we fast to overcome our passions, inclinations and desires so that they may not lead us into sin.
Further reading: http://www.ewtn.com/library/ANSWERS/LENT.HTM