There are those who fast regularly from certain foods, and those who fast occasionally from all food. I think in the Protestant cultures, fasting itself is suspected as being some kind of odd and unhealthy discipline, or a misguided attempt to earn God's favor. (It's sometimes seen as a doubly-misguided effort, if the ultimate fast that God desires from us is justice.) So is there any value at all in fasting?
The New Testament records that Jesus fasted -- and that while he was fasting, he was tempted. Fasting and temptation generally go together ... but I'm getting a little bit ahead of myself. If there were no value in fasting, Jesus would not have fasted, so we should look deeper there. If there is nothing wrong with food, why give it up? Food is a blessing for which we give thanks -- so why not simply give thanks and never go without?
One valuable thing about fasting is the practice and experience of mastering our appetites. Our body has appetites, and in a healthy person we find healthy appetites. Why set aside a healthy appetite? It helps us to know -- not just in our minds but to know by experience -- that even a healthy appetite which is genuinely necessary for life can be safely set aside for a time. We may fast for a meal, or for a day, and on the next day we find that there was no harm done at all. Our appetites are not eager for us to find out that we can safely ignore them for a time. Our habits feel the threat that we were able to set them aside for a day.
Fasting does bring on temptation. It deliberately challenges our
appetites and our habits, and without some practice, those are enough to
give us a struggle. We read that when Jesus was tempted during his
fast, the first temptation involved feeding himself. If you've never
tried fasting, consider it -- and watch how the simple act of considering it
causes your mind to fill with thoughts of whether you really need to do
so such a thing, whether a little food would be so bad, how there's
nothing wrong with food. Do you talk yourself out of it before your
appetites have led you to insult some random medievals or Roman Catholics? (And
of course there's nothing wrong with food. If it were a bad thing, we
shouldn't let ourselves think of it as a sacrifice to give it up for a
time. It's a false argument, of the "straw man" type, to say that fasting implies there is something wrong with food.)
We can practice these small and safe tests of our self-control with our desire for food -- an appetite that really is necessary to survival. If we can master ourselves for a time with an appetite that is so very necessary, how much more can we master ourselves with appetites where our personal survival does not depend on them. If we can see there is no harm done to ourselves or our appetite by this exercise in self-control, we will be more willing to restrain ourselves in other things, more able to see the line between what is a healthy appetite, and what is self-indulgence trying to masquerade as health.