How Fasting Works

Hey look, it’s time for Lent.

Amy Welborn has up a good post, with a sturdy dose of St. Francis de Sales to finish up, “What St. Francis de Sales Wants You to Know About Fasting.”  She made the cool meme at the bottom of this post.

If you are looking for some seasonal viewing Wednesday to help you feel better about not eating, the French documentary  The Science of Fasting is up on Amazon Prime.  The Amazon version has English voice-over and captions, but below I put the trailer to the original French version, since who wouldn’t want to see that just for fun?  Apparently about the time fasting was becoming the hot new non-diet in the US, it was already the hot new non-diet in France.  I was hoping the documentary would be a little heavier on the details of the physiology of fasting, but it’s more of a (pro-fasting) look at using fasting to treat this, that, and the other thing.

Crazy People Pay Attention: Even the pro-fasting Soviet scientists who exhaustively studied the medical uses of fasting made a list of conditions for which fasting was contraindicated.  It doesn’t cure all the things.  It makes some of the things worse.

In the quest for an explanation of the physiology that hit the layman’s middle ground between Buzzfeed and Biochemist, I found this nice slide show on “The Phisiology of Fasting and Fatty Oxidation Defects.”  I found it helpeful.  Also, takeaway point: If you are unable to access stored fuel in your body, fasting is not for you.

Here are some things that were a bit over my head at points, but I liked looking at them anyway:

That last one is a case study on a monk who undertook a 40-day fast under medical supervision.  Note that while extended, medically-supervised fasting was a going remedy for obesity in the second half of last century, it dropped out of popularity when people starting dropping dead (still fat at the time — the deaths were not from starvation).  Here’s a reminder from a physician who is one of the major voices in favor of fasting: If you feel sick, you should eat.

Which brings us around to the Catholic thing.

One Meal and Two Smaller Meals . . .

. . . and all the drinks you can stand.  That’s the USCCB’s instructions on observing your Ash Wednesday and Good Friday fasts.  There are more useful links to follow from there, go take a look.  The 1+2 rule is designed to make the fast manageable for the average working-age Catholic.  Not everyone between 18-60 is obliged to fast, though:

 Those that are excused from fast and abstinence outside the age limits include the physically or mentally ill including individuals suffering from chronic illnesses such as diabetes.  Also excluded are pregnant or nursing women.  In all cases, common sense should prevail, and ill persons should not further jeopardize their health by fasting.

If you need to eat, eat.

But let’s talk about the 3-eats-a-day approach to fasting.  Because here’s what: Even though the rule is designed to make it possible for more people to be able to fast, some people may find it easier to fast by not eating all three sessions.

I know!

But back up to that physiology thing.  When you stop eating, your body goes through three* major phases in its quest for fuel:

  • It works through the fuel from your last meal, if that hasn’t been depleted or stored away yet (instant).
  • It works through your stored glycogen (medium).
  • It starts accessing your fat for energy (longterm).

Each of those involves a biological switching of gears.  Depending on how you time your meals, you may well be almost to the point of using fat for fuel by the time you go to eat in the morning.  You may as a result find it easier, depending on what your body is like, to just go ahead and switch to using stored fat for the rest of the day (drink plenty of non-caloric fluids) and have supper in the evening.

That doesn’t work out as well for everybody. Some people do better with the 2+1 plan.

But I mention it because in my experience, eating a couple small meals just makes the hunger cycle more viciously unpleasant for me, because I happen to have a body that excels at quick packing away all calories from the current meal into longterm storage, and then loudly demanding another feeding.  It’s easier to just have a cup of tea or something to stave off the relatively more mild hunger that comes with not eating at all, do something distracting during the day, then eat well at dinner, done.

If you worry that I have taught you a way to suffer less and now your Lent might not be Lent-y enough, keep in mind you can always go scourge yourself or something if you find your fast days too easy.  Or give money to the poor.  Not to get completely wild, but if you wanna suffer, that is an option.

*The fourth phase is where you’re out of fat and your body starts tearing itself apart in a last-ditch effort at survival.  If you are already poorly provided-for in the fat-department, fasting is not for you.

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Related: If you are one of those people who could happily be vegetarian all but two days of the year, or you could never ever happily be vegetarian, here’s my tutorial on thwarting the meat demon. Other past Lenten tutorials:

The main thing: Just do the thing.  A good Lent is unlikely to be a perfect Lent.   If all you can manage is a humble Lent, you’re ahead of the game.

Lent 2016

Image courtesy of Amy Welborn, used with permission. Click through to see the original post where it appeared.