Fasted Running

Not ‘Fast Running’, or ‘Faster Running’ – but ‘Fasted Running’.

Like running when you haven’t eaten for a long time.

This week I experimented with running fasted.

Why?

It’s a long story.

Shall we start at the beginning with some historical exposition?  Or should we jump into Act Two where I’m wondering what all these fast proponents are talking about…

“Oh, fasting gives you mental clarity!”

“Oh, fasting gives me so much more energy!”

“Oh, fasting changed my life!”

What a crock of…Shiver me timbers!

I did not get any of that.

Ok, Let’s get back to the ‘why’.

I’m coming off a long-term injury and my weight hasn’t come back down to where I was a couple years ago before the injury.  So, I’ve been focused on nutrition and trying to eat healthy, and yes, lose some weight.

I‘m currently training for an ultra.  And I’m about to go into some higher mileage weeks.  My fear, and partly my experience, is that training heavy is going to cause additional injury if I don’t go into it a bit lighter.

My logical mind created a plan to have my training ramp up as my weight ramps down.

But that has not happened.  Even with the clean diet, my weight has stubbornly stayed about 10 pounds higher than I want.  I guess it’s a combination of being older, and having trained my metabolism to such a low idle over the last couple decades – but, bottom line, I was stuck.

I was frustrated.  I needed to do something different.  A shock to the system.

And since I had a down week on the schedule, I asked my coach to work in a couple fast days.

…

I have done fasting before in my adventures.  I find I can handle a 24 hour fast easily enough.

What I do is simple.  When I wake up, I don’t eat all day until the next morning.  I drink coffee, tea and water.  I find this works the best because I’m not hungry when I wake up and my stomach is already empty.

Around lunchtime I may start getting a little hungry, but that’s easy enough to get through.  Then, later in the day I find I’m not hungry, but I am thinking about food, more out of habit than anything.

And that’s it.  A simple 24-hour fast.

What does it do?  For me each of these 24- hour fasts results in an initial 4-5 pound impact on the scale.  But that is not the net loss.  Once I start eating again it bounces back a bit.  The net loss ends up as 2-3 pounds.

What else does it do?  Well, the proponents of fasting ascribe everything from endless life and total consciousness – like it’s some sort of religious-emotional orgasm.

For me it’s a way to break a plateau and potentially give my metabolism a jolt.

…

This week was a bit different because I did workouts at the end of the fast period, before I started eating again.

What I wanted to do today is answer the question:  “Should I run fasted?”

This also appealed to my vein of Stoicism, where you create scarcity as part of your practice to prove to yourself that it is not to be feared.

…

But, first, how do I feel during the fasting process?

It’s not terrible, but it’s not great either.

First, I’m not hungry.  Starting in the morning, my stomach is already empty.  I really don’t get hunger pangs.

Second, physically I don’t feel too bad.  I’m doing these fasts on rest days so there is no workout to contend with.  Maybe I’m a little lightheaded, maybe I’m a bit less energetic, but nothing terrible.

My stomach is a bit rumbly, probably from the coffee.  My mouth gets incredibly dry and gross.  I find my skin feels greasy from whatever is going on – like I’m sweating fat.

Third, mentally, I think this is where it hits me the most.  It’s like the feeling you get when you do a keto diet.  It sucks the glycogen out of my brain and just makes me stupid and fuzzy headed.  I can’t be creative at all with this fuzzy head.  Verging on a headache.

Finally, it makes me want to sleep.  I feel like I could lay down and not move for hours on end.  ‘Listless’ is what I would call it.

Sounds like fun, right?

I didn’t transcend consciousness or see God.  I just felt blah.

I did this twice this week.  Wednesday and Saturday.  Both were rest days, so nothing more strenuous than walking the dog.

The real event was waking up that second morning, fully fasted and going for a run.

I did this on purpose to see how my body would react.  I’m a curious guy and thought it would be an interesting experiment.

This was where my body was talking to me.

First thing you notice is that you have zero energy.  You know the last 3 miles of that marathon or half marathon where you went out too fast and hit the wall?  You know that feeling where you can’t lift your legs?

Yeah, that.

Wednesday, I did a 6ish mile trail loop on my home course.  A base building easy run.  Usually, once I warm up, I settle into the run and my second half is better than my first.

Not when fasted.

Halfway into the run I hit the wall.  Nothing in the tank at all.  I ended up walking some hills and really suffering.  I consoled myself that I was practicing for the ultra.  Because, in an ultra you will have these long periods where there is nothing in the tank and you need to figure out a way to keep going.  I got slower and slower over those last 3 miles.

What specifically did I notice?  My legs had no pop and no energy.  I was achy.  Achy in the joints and achy in my muscles.  All my muscles. Even my arms and shoulders.

The other thing I noticed was that, even though it was a nice morning, not too hot, I drank my entire liter bottle of water and could have used more.  My guess is that fat needs water to metabolize.

So – pro tip – if you’re going to run fasted, drink a lot of water.

Saturday, I fasted again, same way for 24 hours and did my Sunday morning run before eating anything.

In general, I thought Saturday was an easier day then Wednesday.  Same symptoms.  Muddy head, wanted to sleep.  But my body didn’t seem as upset as it was Wednesday.  I can’t quantify it, but I think maybe my body was already adapting by the Saturday fast.

Sunday morning I woke up late.  Fasting makes me sleep more.

It was drizzling.  The dog and I went to Starbucks for some coffee and then to the trailhead.  This one I ran on the Cape Cod rail trail which is a very flat and forgiving course.

My experience was the same.  No energy.  Achy.  And about halfway in I hit the big wall, then a continuous deterioration into the finish for 7 ugly miles.

OK – so what is the answer to the “Can I run fasted?” question?

The answer is ‘Yes, you can, but it’s probably going to suck.’  Even the easy, base-building runs I’m doing sucked and felt like they were damaging.  There’s no way I would have done any actual tempo or speed or strength training while fasted.

Frankly, I’m not sure I’d recommend it.  It sure felt like I was putting a lot of stress on my body.  I’m not sure that’s positive stress, especially at my age.

I think there’s a fasting hangover as well.  You don’t feel quite right for a couple of days.

And, I don’t know if it was purely coincidental, but I had a couple emotionally low days after the fasts as well.

If we say we should listen to our bodies, I’m pretty sure my body is telling me not to do this.

Your body may tell you something different.  We all have different machines.

But that was my experience with fasting and running while fasted.