Fasting is traditionally thought of as setting aside a time to go without food so that you can focus your time and energy on the Lord. Prayer and Fasting usually go together.
I don't remember a command in the New Testament telling us that we should fast. But I do know that Jesus went off by Himself to pray, often early in the morning hours. Jesus shows us how important it is to stay connected with God the Father.
The last time I tried to fast for a day was not pretty. I was at a marriage retreat and told I had to try it. My blood sugar went down and my rebellious self came up. (My wife Joan could tell you about it.)
There may be some other options when it comes to fasting. Maybe you could set aside an evening to leave the TV off and spend that time reading God's Word and praying. Or you could eat a lite lunch and go off by yourself.
I spend time in the morning reading my devotions, writing this blog on weekdays, and praying before I break my overnight fast and have breakfast. It works for me. Something else may work for you. The important thing is that we remain connected to the Lord all week long, not just when we worship Him on the weekend.