Running Carb-Depleted

sarah cuff Carb-Loading for Runners, Nutrient Timing, Training 6 Comments

In my Eat 2 Run nutrition practice I am constantly stressing the importance eating enough carbohydrates to order to have enough energy to perform well. However, withholding carbohydrates strategically at certain times can actually benefit your performance. By practicing carb-depleted training runs, you might very well take your training and race performances to the next level.

Let’s take a look at why anyone would care to run on empty, who this type of running is best for, and how to practice carb-depleted runs properly.

The Why 

wallBy training your body to burn more fatty acids as fuel (instead of glucose, aka carbohydrates), you greatly decrease your odds of hitting “The Wall”. In other words, you will be able to run further while taking in less fuel. I personally experienced this when I ran my best marathon time ever on the least amount of fuel ever (one gel, to be exact).

So by limiting carbohydrates before/during running, you increase your fat-burning capacity – in fact Matt Fitzgerald points out in his book The New Rules of the Marathon and Half-Marathon Nutrition, a previously sedentary person who participates in a 6-week training program using sports drink during each workout increases his/her fat burning capacity by 5%. However if that same person in the same program abstained from any sports drinks or carb sources during the workout, he/she would would increase his/her fat burning capacity by more than 20%.

Additionally, research shows that carb-depleted training can boost the capacity of our muscles to store carbohydrate by up to 50 percent.

The Who

I find this type of training is best for those with a history of “hitting the wall” and those who have trouble consuming energy gels/drinks (due to GI distress, etc) while racing.

However, I don’t typically recommend this method of training to new runners. It is better suited to experienced half, full or ultra marathoners who wish to train their bodies to burn more fatty acids instead of carbohydrates while running. Because you begin the workout already carb depleted (and can further enhance this depletion by eating only a light dinner the night before) and abstain from taking in any carbs throughout the run, it probably won’t feel great and you may struggle through your run (those brand new to exercise run the risk of feeling dizzy, sick or even fainting if they attempt this). However, your body adapts and it feels easier as your body learns to burn more fatty acids as fuel.

Personally, I have a hard time putting too much fuel into my system while racing, so I add carb-depleted runs to my schedule in order to allow my body to perform well off of less fuel.


The How

Carb-depleted training can either be done first thing in the morning (after an overnight fast of 10 hours or more), or by choosing to withhold carbohydrates between a morning and an afternoon run. While the second option may rarely be appropriate for anyone other than elite runners (who train full-time), morning carb-depleted runs are relatively easy for anyone to implement.

Note, you’ll want your run to last about 1-hour (up to two hours), first thing in the morning without consuming any carbohydrates before walking out the door. Running carb-depleted for much less than an hour upon waking doesn’t appear to allow for the desired adaptations.

Although you ideally want your carb-depleted run to last at least 1-hour, start with only 30 minutes to allow your body to adapt. Begin with one carb-depleted run per week, and after a few weeks once running one hour carb-depleted feels good, you might add a second. If you’re really ambitious, you could choose to add a 30-minute or so tempo portion into one of your carb-depleted runs!

If you do decide to practice carb-depleted runs, just ensure that when race week rolls around, you stop – no more carb-depleted running. The entire week before race day your focus should be on ensuring you go into the race with full glycogen stores and therefore you’ll want to ensure you go into each run well fuelled.

Last but not least, the minute you finish a carb-depleted run, it is imperative you have a recovery shake immediately (or at least within 30 minutes). This form of training can be stressful to our bodies and our hormonal systems, and withholding recovery nutrition after such a challenging workout would be less than desirable.

By practicing carb-depleted runs, you might very well never hit “The Wall” again!

Eat clean, run strong, be well… Cheers, Sarah  |  Sarah J Cuff, RHN

Image 3PS. Check out Devon McGuire’s amazing transformation story – she came to me with with a history of disordered eating, restriction and nearly obsessive calorie counting and tracking. She knew she needed to improve her nutrition in order to perform well in her upcoming marathon (in which she’d set herself an ambitious goal of sub-4 hours)… But she didn’t know where to start. Click here to find out the changes she experienced and how she did in her marathon.

Comments 6

  1. This is very very interesting, thanks for posting! I do all my workouts in the morning so be it a run or going to the gym, it is effectively done “on empty”. I never eat anything beforehand. During the exercise I only drink water, sometimes with an electrolyte table added if it is very hot. I usually run for at least an hour but once weekly (last week I did 21km both Sat and Sun) I do a minimum of 21km run – also on empty. The longest I have done is 30km – again on empty. My body seems to have adapted to this and I don’t hit a wall and even water I only need when it is very hot. What I really need to work on is making sure I have that recovery shake or just SOMETHING when I get home. Usually I just grab a drink and don’t feel able to eat for hours.

    1. Post

      It sounds like you’ve been practicing carb-depleted training without even realizing it!! Do you race half-marathon’s? And yes, you’ve got it – do ensure to refuel well after those runs, will help you to recover SO much faster! Make up the recovery shake in advance so it’s ready to just pull out of the fridge and drink 😉

      1. I don’t race – for me it’s not about the competition with others. Good idea to make the recovery shake in advance – that’s probably the only way I will be able to get it down me. 🙂

  2. Thanks for this info. I need to learn better nutrition for runners in general. I’m starting half marathon training soon and really want to do it right this time.

    1. Post

      Hi Jacquie! For sure, by practicing good nutrition as well as proper nutrient timing, you’ll find you have more energy for your training and you recover faster/better. Good luck!!

  3. Pingback: Fat-Loading for Race Performance (part 2) | Eat 2 Run

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