The will of God seems clear about fasting. He likes it. And he honours it as well.
The Old Testament is replete with references to fasting, both individual and corporate. Again and again, in times of trouble, the leader of the people would call for a fast. The prophet Joel issued a striking summons. "Blow the trumpet in Zion!" he proclaimed. "Proclaim a fast. Call an assembly. Father the people. Notify the congregation. Assemble the elders. Bring the children, even infants at the breast." (Joel 2:15-16)
Things didn't change when Jesus came to earth. He fasted himself. When he was led out to the desert to be tempted, "he fast forty days and forty nights." (Matthew 4:2) He took it for granted that people would undertake occasional or even regular fast. He gave counsel about it.
"When you fast," he told them, "do not look gloomy the way the hypocrites do. They change the expression on their faces so that others may know they are fasting. They are already repaid, I assure you. But when you fast, have your hair groomed and your face washed. That way, nobody will know you are fasting except your Father whom you do not see. And your Father, who sees all things done in secret, will repay you." (Matthew 6:16-18)
It does indeed seem clear. The Lord wants us to fast. He wants us to do it without fanfare. And he honours it.
That should surely be enough for us. If God wants it, we'll do it. But it would probably help if we understood it.