Carb Depletion

I recently cut a juice fast short by a day or so in order to make sure I was ready to continue my marathon training, but I knew that three regular meals was hardly enough food to fuel a 17 mile run.  Given this fact, I decided to turn my regularly scheduled training run into an experiment in carb depletion, and ultimately a lesson in carbo-loading.

Getting by with a little help from some friends

Getting by with a little help from some friends

Carb depletion is what happens when your body runs out of the glycogen it needs to convert into energy. Normally when this happens, a runner is said to be bonking.  Bonking is the point at which your body simply refuses to work because it does not have the necessary fuel to operate properly.  The visual of bonking can be pretty disturbing, an athlete whose arms and legs refuse to respond properly to the brain’s commands, instead stutter and flail as he or she struggles even to remain standing.  This is something that all athletes want to avoid for obvious reasons, but for me, I was curious just how far I could get in a carb depleted state.

So here are the basic parameters of my little Saturday morning running experiment.

  1. I stopped eating solid foods on the preceding Sunday night.
  2. I ingested nothing but juice, water, and vegetable broth for about 96 hours.
  3. I broke my juice fast Thursday night with a small salad and a 1/2 cup of quinoa and avocado.
  4. On Friday I had Juice for breakfast and a mid morning snack followed by another 1/2 cup of quinoa and avocado.
  5. Friday’s dinner was a bowl of grilled veggies, black beans, and rice.
  6. Saturday morning, before the run, I had morning running day breakfast of a piece of gluten free toast with peanut butter and honey along with a natural pre-workout mix.
  7. About an hour after my toast, I started running.

I was admittedly apprehensive when I got started and intentionally kept my pace slow to conserve energy.  After about the first mile I got comfortable and was surprised by how well I felt, but this feeling only lasted the first hour. At this point I started to feel tired and a bit run down, which normally doesn’t happen to me this early.  At an hour and twenty minutes into my run I was already desperate for fuel so I started in on the gels.  Normally I start with the gels around 1:30, and not out of a sense of desperation, but of careful planning, since my pre-workout formula works so well. I knew then that this run was going to be difficult and likely shorter than expected.

'I only need one more minute...'

‘I only need one more minute…’

When I do start using gels in my runs, I usually take one about every 40 minutes.  On this day, I was needing to take them every 25-30 minutes.  I kept pushing to move forward but it got harder and harder after 2 hours. Two and a half hours in I was totally spent. The gels stopped working. My legs felt like jello. I felt empty inside.  I started to get a little shaky, but I couldn’t even force down another mouthful of gel or. I pulled up and started to walk to allow my body to rest while continuing to make a little progress.  From that point I probably had another mile, maybe two, before I absolutely crashed. Rather than push myself up to and over the edge, I decided to call it day and end my training run early.

They say that your body, when properly fueled can carry you for 20 miles.  My body, when depleted of fuel could only get me about 6.5 miles.  Supplementing my energy with gu’s and gels and blocks got me an additional 6.5 miles before I was exhausted.  So the math would suggest that with proper fueling, I would have been able to cover the first 20 miles on my own and then my body would have been able to push through the final 6.2 miles on supplemental sugars and a little bit of guts. That’s just enough to get to the finish line.

Jason Argabrite

As a Certified Nutritional Counselor, Product Formulator, and avid Runner, I am passionate about all aspects of personal health.

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3 thoughts on “Carb Depletion

  1. Alyssa

    We call it bonking in the cycling world too. I came thisclose to bonking on my first 40 mile ride because I skipped the refueling. I learned never to do that again.


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