Pope Francis has proclaimed a voluntary fast this Saturday for peace in Syria. I plan to observe it, and I implore anyone who reads this to join the Holy Father in this. You don't have to be Catholic, or indeed a Christian, to do this; think of it as an act of solidarity with the suffering there, if you like.
Why fast, for Syria or anywhere? Here are four reasons:
1. Pope Francis asked us to. Not a binding reason, even for Catholics (since the fast is not an obligation but an invitation); but for those traditional Catholics who've been complaining that he isn't pontifical enough, and for those progressive Catholics who've complained that the Church doesn't show enough compassion for the suffering, here His Holiness is doing both. And even if you aren't a Catholic, he is an awfully nice man, so it's only polite to go along with it, don't you agree?
2. Fasting is a way of entering more profoundly into prayer. The Scriptures consistently associate prayer with fasting, and Our Lord presumes that His disciples will fast. Like kneeling or making the sign of the Cross, it is a sort of way of praying with the body as well as the soul; since we are souls and bodies at the same time, this is not only logical, but an enrichment of prayer. And we should be praying for Syria whether we elect to fast or not: the conflict is a ghastly one, and will likely be protracted even if the United States intervenes.
3. It is one way of showing solidarity with the suffering. It must be admitted that, since we are half a world away, this solidarity does not in and of itself help them. At least, not in any visible way; I don't profess to know what God does with the spiritual energy, if any, involved in fasting. But solidarity is good for us. It reminds us of what we too easily forget in our insanely easy lives, the real and bitter hardships that most people experience. That lesson in empathy can improve our character, and make better and more obviously efficacious acts possible to us. A simple fast may not sound like much, but after all, you have to start where you are -- and I'd lay fifties to any amount that a majority of Americans, perhaps even of American Christians, have never fasted.*
4. It is a symbol of nonviolence. Not that eating is a symbol of violence (unless you've watched Man vs. Food lately), but protests in the form of hunger strikes are a long-standing tradition of civil resistance, as exemplified in figures like Mahatma Gandhi, Cesar Chavez, and Venerable Dorothy Day. In contrast to strikes, or even sanctions, a fast is an act within oneself, and as such appeals to the opponent's conscience instead of his passions or appetites. Appeals to conscience are only too rare in our age, because, being accustomed to power, we subconsciously suppose that force will achieve peace; but the two are radically and intrinsically opposed. And as we suppose that no appeal save the appeal to force will succeed, we erode the power of the heart to respond to anything else. The determined refusal to appeal to anything except conscience, then, becomes a means of awakening and strengthening conscience; and if they harden their hearts, then we join with Jesus in weeping over a city that knew not the time of its visitation.
The normal rule for a Catholic fast (as observed in the Roman Rite, which encompasses most western Christians) is that one ordinary meal is allowed, as well as two snacks that are both less than half a full meal. That is the minimum; going further is of course permitted. It is traditional to abstain from meat on a fast day as well. Obviously the rule is defined relative to how much one normally eats, so there will be variation from person to person.
*Yes, counting Catholics. This is less because of the lax state of Catholic morals in this country, than just because Catholics are a (large) minority of Americans and a (larger) minority of American Christians.