I've never participated in Lent; I like the idea but the biblical mandate for it really hasn't ever been explained to me well enough. The demand from God for a fast in Isaiah, however, is one that I like:
"Is not this the kind of fasting I have chosen:To think! If every Christian accepted this fast for 40 days, what a difference we could make in the world! More of a difference than, say, giving up soda or video games for a month.
to loose the chains of injustice
and untie the cords of the yoke,
to set the oppressed free
and break every yoke?
Is it not to share your food with the hungry
and to provide the poor wanderer with shelter—
when you see the naked, to clothe him,
and not to turn away from your own flesh and blood?
- Isaiah 58:6-7