Running in a Glycogen Depleted State Lets Your Body Access Fat Stores

Are you in the midst of training for a half or full marathon? If the answer is yes, I’m guessing that carbohydrate gels are a big part of your training routine. Even if the answer is no, there’s probably a good chance that you consume these gels, chews or other such supplements to get through your runs.

While these gels have a place in long distance run training, of late, runners have been overusing them, believing they need the supplements for even short runs. That overuse comes with some heavy consequences.

Here’s the deal: Our bodies are designed to run on either sugar or fat. Sugar, or glycogen, comes in very limited stores. Fat, on the other hand, is available in a nearly endless supply. The trick is to teach your body to access that fat. When you overuse carbohydrate supplements like gels, your body doesn’t get the chance to learn this and it fails to access fat for fuel.

The result of this inability to access fat in a race or a long run is what’s classically known as a bonk. The result of the inability to access fat on a regular basis is slower running and unwanted calories.

So when and where should you use gels and how do you break your dependence on them? You train your body to access fat by practicing runs in a glycogen depleted (GD) state.

Let me be upfront about this—learning to run in a GD state isn’t fun at first, but it pays off. And before jumping in with both feet, I’d recommend gradually reducing your dependence on gels by extending the period of time you go without them by a mile or two at a time.

Once you’ve successfully been able to run about 90 minutes or so without using a carbohydrate supplement, it’s time to take things a step further. What you want to do is head out for a GD run first thing in the morning without consuming any calories. Then complete all the miles without supplementing, other than with water.

To really get your body burning the fat stores, you need to eventually be able to run between two and two and a half hours without fuel. Once you’ve mastered this, and as you approach your race day, begin alternating runs with and without fuel. Your body will have learned to tap into fat after about four to six weeks of this type of training. The reason you’ll want to start alternating runs with and without fuel is that you will want to use gels during your long race and you’ll want your GI system primed to handle them.

A couple of final tips:

  • Try to start the GD runs with a cup of coffee to give yourself a little glycogen-free boost
  • Don’t go over about the two-and-a-half hour mark in a GD state
  • Have fuel ready to go at the end of a GD run so that you can immediately replenish and help recovery
  • Take your GD runs out at a VERY easy pace—this is how you will get through them

Once you’ve mastered the GD run, both your race times and your waistline will thank you!


Amanda Loudin is a freelance writer, running coach, and the voice behind the MissZippy1 blog, a site for runners seeking experienced advice, the latest running news, and a fun exchange of all things running related. Follow her on Twitter, Facebook, or Instagram at misszippy1.

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