My parish priest is Fr. Chris, who also is an administrator of this Web forum. I like the way he explains fasting in his sermons. He always says, "the reason we fast is that we want to learn how to love."
Love is always, inevitably, about restraint and self-denial. We are dealing with people who are very diverse and who have needs often contradicting to our own needs. If I am dealing with a person who says, "you know, I need this and this and that," and I say, "but *I* have a different need, so I don't care what *you* need!" - that's not love. I am really loving someone if, and when, I deliberately forget about my own needs (or restrain them, put them on a back burner), and concentrate on that other person's needs.
Fasting is a discipline, a training in self-restraint and self-denial. An Orthodox Christian who really fasts learns to develop in him/herself this "nothing urgent" attitude, like, "OK, this steak looks and smells great, but it's not THAT important - I might eat it some other time." It's a small thing, of course, but Christ does give us the idea that all these "small things" are important teaching tools. If I cannot restrain myself from eating steak today, shall I be really able to restrain myself from judging others, gossiping, boasting, causing pain?
I am sure that there is a lot about fasting in the archives of this forum, and you can find a lot better explanations there, but I just thought I should share.
Best wishes to you,