Cleaning House

Fasting is everywhere right now. A few guys in the room have done a 72-hour fast this year, a few more are planning one, and people in my life outside hockey are doing them too. Almost no one doing it can tell you exactly what it does to the body. So I looked into it.

Your body runs in two modes. When you eat, it builds. Muscle, tissue, energy stores. When you stop, it flips into repair, clearing out old and damaged material and recycling it instead of building new.

A fast just holds you in that repair mode.

Getting all the way there takes time. Around 24 hours you burn through your stored sugar and start running on fat. Around 48 hours the deep cleanup kicks in and your cells start clearing out damaged parts. By 72 hours you're fully in it.

That's why it's three days. Anything shorter and you don't fully get there. Anything longer and you start paying for it.

Here's the trade. While you're in repair mode, you're not in build mode. So you lose muscle.

Your body breaks down lean tissue to keep itself fueled. A few pounds over three days is normal. You get most of it back when you eat again, but for those three days you're going backwards on the thing most athletes work hardest to protect.

That's the part the videos skip.

Repair mode is only worth as much as you have to repair.

A body fighting disease or carrying decades of wear has a lot for the cleanup to do. The most cited study on this comes out of USC, and it was run mostly in mice and in cancer patients on chemo. People whose bodies had real damage to clear.

A healthy 24-year-old who trains and eats well doesn't have much built up. The cleanup still runs. There's just less for it to find.

My dad is the clearest example I've got. He did a 72-hour fast last year while dealing with cancer and trying to avoid chemo. The most legitimate reason to do this I can think of, and he did his homework first. When I asked him what it did, he said he couldn't really say he felt any big difference, but nothing was bothering him either.

The guy with the best reason of anyone, and he still couldn't point to it.

There's one thing everyone who's done it agrees on. You feel sharp.

My dad said he felt very alert. The guys in the room talk about brain fog lifting. It's the part people actually notice.

It comes from the fuel switch. Once you're running on fat your brain burns ketones, a cleaner, steadier fuel than the blood sugar swings you get from eating all day. Your body also dials up its alertness while you're fasting, an old survival edge from when food wasn't guaranteed. The morning coffee a lot of guys have through it adds to the effect, but the clear head shows up either way.

For a healthy athlete, the trade is real muscle for a cleanup your body doesn't have much use for yet. In-season that's a bad deal. At the very start of the off-season, when you're doing nothing and a little lost size costs you nothing, it's a closer call.

I was planning to do one myself. I wanted to understand why before I put my body through it, and that turned into this. Then life got in the way, training started back up, and three days without food doesn't fit anymore. The window would've been those first weeks off, before anything ramped up.

That's the window for anyone thinking about it. Now you know what you'd actually be signing up for.

Go eat, see you in two weeks!

— Ethan Edwards

Natural Athlete Co.