A priest from Peru I once had the good fortune of meeting described his religious community’s periodic fasts to me this way:
Though we possess the means to continually feast, we choose to regularly fast so that those who continually fast without choice might be permitted to regularly feast.
While it is true that fasting has built into it the purposes of cultivating self-mastery over disordered appetites, facilitating the spirit of prayer or creating in the heart an attitude of sacrifice toward God, in Judaism and Christianity it was most intimately tied to the anti-individualist understanding of possession and ownership, i.e. the goods I possess are meant to benefit others, and because essential to my fulfillment is my neighbor’s fulfillment I will regularly deny my possessiveness to the point of discomfort in order to benefit in some way my neighbor whose need lays just claim on me.
This is clearly what Isaiah was getting at in 58:5-8:
Is this the manner of fasting I wish, of keeping a day of penance: That a man bow his head like a reed, and lie in sackcloth and ashes? Do you call this a fast, a day acceptable to the LORD? This, rather, is the fasting that I wish: releasing those bound unjustly, untying the thongs of the yoke; Setting free the oppressed, breaking every yoke; Sharing your bread with the hungry, sheltering the oppressed and the homeless; Clothing the naked when you see them, and not turning your back on your own. Then your light shall break forth like the dawn, and your wound shall quickly be healed
This all also reminds me of a quote from the Lenten breviary that I love:
Prayer, mercy and fasting: These three are one, and they give life to each other. Fasting is the soul of prayer; mercy is the lifeblood of fasting. Let no one try to separate them; they cannot be separated. If you have only one of them or not all together, you have nothing. So if you pray, fast; if fast, show mercy; if you want your petition to be heard, hear the petition of others. When you fast, see the fasting of others. If you hope for mercy, show mercy. If you look for kindness, show kindness. If you want to receive, give.
— St Peter Chrysologus (c 380-450)
So this Lent when you lessen your feast to make room at your table, bring with you to the next Mass you celebrate the joy of having imitated the Master who invites you to a Feast spread before you at the cost of His own once-chosen fast.