Is it necessary to fast or to give something up for God?

Answer:

"Therefore, if you died with Christ from the basic principles of the world, why, as though living in the world, do you subject yourselves to regulations -- "Do not touch, do not taste, do not handle," which all concern things which perish with the using -- according to the commandments and doctrines of men? These things indeed have an appearance of wisdom in self-imposed religion, false humility, and neglect of the body, but are of no value against the indulgence of the flesh" (Colossians 2:20-23).

Where in the New Testament does it say that God asks you to give up something or to fast? God defines what He wants as the worship of Him, not men. "I marvel that you are turning away so soon from Him who called you in the grace of Christ, to a different gospel, which is not another; but there are some who trouble you and want to pervert the gospel of Christ. But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed. As we have said before, so now I say again, if anyone preaches any other gospel to you than what you have received, let him be accursed. For do I now persuade men, or God? Or do I seek to please men? For if I still pleased men, I would not be a bondservant of Christ" (Galatians 1:6-10).

It is true that men have long decided that in order to get a god to listen to them, they had to suffer in some way. You see this when Elijah challenged the prophets of Baal. When those false prophets wanted Baal's attention they cut themselves in the mistaken belief that suffering would get Baal's attention. "So they took the bull which was given them, and they prepared it, and called on the name of Baal from morning even till noon, saying, "O Baal, hear us!" But there was no voice; no one answered. Then they leaped about the altar which they had made. And so it was, at noon, that Elijah mocked them and said, "Cry aloud, for he is a god; either he is meditating, or he is busy, or he is on a journey, or perhaps he is sleeping and must be awakened." So they cried aloud, and cut themselves, as was their custom, with knives and lances, until the blood gushed out on them" (I Kings 18:26-28). The worship of Molech was worse. There the worshipers thought that the more valued thing was offered up to Molech, the more likely Molech would answer their plead. That is why you read about people doing horrible things, like offering up their own children. "But he walked in the way of the kings of Israel; indeed he made his son pass through the fire, according to the abominations of the nations whom the LORD had cast out from before the children of Israel" (II Kings 16:3).

The idea that one needs to give up food or something of value to them to get God's attention is the same mindset.