Low Carb Endurance Training

Let’s talk about low carb endurance training. I have been hearing more and more about the topic lately and I’m sure it’s because of my interest in said topic but you know what they say, what you seek is seeking you.


I’ve been a big fan of the Paleo style diet since I tried it about a year ago. My first experience was the 21 Day Superhero Challenge, which is a Paleo based diet/cleanse that did with a friend who happened to be starting a new 21 day challenge about a month before my wedding. I was regularly working out 4-5 days a week but figured, what the hell, why not try something new to lose a couple of pounds before the big day.

I did lose a couple of pounds but more importantly I felt *AMAZING*.

But…only after getting through the initial adjustment period.

I always thought of myself as a pretty healthy eater but I went through major withdrawal from sugar when I started a Paleo style meal plan. I was shocked. Where was all of this sugar coming from?! I had watched the documentaries and I already cut out most processed foods, right?

Hello! As a vegetarian I was eating a ton of carbs, grain, flour, soy, and once you start really looking at labels you know that there is sugar in everything. Bye, Sriracha!

By day 4 of the challenge I pretty much thought I was dying. I was exhausted, irritable and I had no stamina or focus. I took it to Google, “Can you die from the Paleo diet?”. I learned that I was experiencing textbook sugar withdrawal. It was crazy to me. How I have I been unknowingly putting so much sugar into my body that I am having this meltdown??

So I toughed through and after the first week things got easier and after 21 days of the strictest diet I’ve ever followed I had the following takeaways:

  • I felt great
  • I felt strong
  • I wasn’t hungry all the time
  • Eating clean is easy (and it makes you a better cook)
  • Paleo food is fucking good
  • Food companies are literally drugging us with sugar and additives

Besides the occasional pizza or pasta dish (I am Italian after all), I was hooked. I’ve been primarily on a Paleo diet for almost a year now.

I found it fairly easy to maintain the diet until I started training for the half marathon in February. Once I ramped up my workouts, it felt like what I was eating was no longer sustaining me. I experimented with adding whole grains, eating more food overall and even trying some meat.

None of the above “fixed” the problem. I thought, there has to be a way to achieve the trifecta I am seeking – Paleo – Vegetarian – Endurance Athlete. I am still in the midst of experimenting to find the right balance for me, especially as I begin training for a full marathon. It’s been an interesting learning process so I’m going to share some of it with you here.


Keeping this book close at hand!

I’m thrilled that so many people are talking about low carb endurance training. The mainstream standard is still to shout “Carb Load!!!” when talking about an effective diet for runners. I even fell prey to thinking that was the only way. I’ve been learning a lot about the science behind how different nutrients fuel the body and it turns out there is a lot of research showing that a low carb diet is not only possible but can be super effective for endurance athletes.

For the rest of the post I’m going to stop using the word Paleo because I don’t want to limit myself to any constraints. Instead I am going to say “low carb” which is essentially the same thing but I feel allows for a tiny bit more leeway. I also want to be clear that this isn’t Atkins Diet low carb where carbs are often replaced haphazardly so while you’re not consuming carbs and will lose weight, you are not achieving sustainable health.

Here’s a little science behind how a low carb diet can be effective for endurance athletes. The key behind low carb endurance training is to increase intake of good fats. I will leave the exact science behind this to the scientists, but here are a few examples of foods that contain good fats:

  • Avocado
  • Coconut
  • Nuts and Nut Butter (not peanuts)
  • Olive Oil
  • Eggs
  • Seeds
  • Salmon and Tuna
  • Lean Beef and Pork
  • Cheese (not paleo)
  • Tofu (not paleo)
  • Edamame (not paleo)
  • Greek Yogurt (not paleo)

When you lower your intake of carbs and increase your intake of good fats, your metabolism actively changes to start burning fat instead of carbs because the carbs are no longer available as fuel, aka Ketosis. Why does this matter with respect to endurance training?

Carbs are stored in your body as glycogen which serves as the primary fuel source for humans and animals when it is available. Only a limited supply of glycogen can be stored in the body at one time. The body can store up to 2,000 calories of glycogen at a time which translates to about 90 minutes of endurance activity. If your body is trained to run on glycogen, you will crash when you run out. See Bonking as related to endurance sports.

Body fat provides a reserve of calories that can be up to 50x more, or up to 100,000 calories. Therefore, when you train your body to switch to burning fat rather than burning glycogen, it should increase your overall endurance. The process through which fat is broken down into energy is a multi-step process so it burns slower and more sustainably than glycogen. Meaning, you don’t have to fuel up as often – you are no longer stuck in a cycle of carbs in, energy out.

Related to this, the concept of train low/race high is a plan that requires you to achieve a fat adapted state during training but then you can consume carbs before a race for added fuel. In theory you will start to burn fat after you run out of carbs rather than hit the wall. No bonk.

Another benefit of a low carb diet to endurance athletes relates to recovery. This diet is anti-inflammatory as carbs and sugar are known to cause inflammation. When you are not consuming carbs and sugar, your recovery time can be accelerated as it will take less time for the muscles to return to normal. Though, this doesn’t mean you shouldn’t rest!

Since I was primarily Paleo when I started training for my first race, my body had already made the switch to burning fat. Knowing what I know now, I can conclude that I was not consuming enough fat to sustain the diet as I added more/longer activity.  Of the good fats that I listed, I was eating maybe 5 of them? No meat, no dairy, no soy, no cheese. I don’t want carbs! but this is why I ended up turning back to them during training. Now I know that there’s another option.

I’ve never been one to adhere to a strict diet but I’ve always had food sensitivities and things that I don’t eat because, plain and simple, they make me feel like crap. While I love the concepts of Paleo, I’m not sure if it works for me in the strict sense. That’s ok! What’s really important to me is to eat the most natural foods that I can. I’ve incorporated some dairy including full fat cottage cheese, plain greek yogurt, cheese, and some grains including quinoa and black rice, strategically into my diet.

I’m making sure that I maintain a primarily low carb (and Paleo focused) diet and keeping the barometer set on how I feel. When I’m following course I feel strong, clear headed, I eat less and make better food choices, and my recovery time is shorter. It can be a lot of work but once you get over the major hurdles the payoff is exponential.

Note, I have no background in nutrition. I am only summarizing and sharing my personal experience in this post. Here are some resources that I have found immensely helpful in my journey and where I’ve learned a lot of the information discussed here. Check them out. 




2 thoughts on “Low Carb Endurance Training

  1. I do this!! I basically eat Paleo, although I’m not into rules, and I of course have cheat days, and I eat beans as well. It’s worked great for me up to the half distance, but I keep on wondering whether I’m going to have to add in more grain as my distances get up there. My mom is a holistic nutritionist so i always work with her when it comes to diet. She and I are gonna look at some things and see if I need to change anything for training–will be a lot of trial and error i am sure! Great post lady! x

    Liked by 1 person

    1. That’s amazing that you have a nutrition coach so close to home!! I do love cheat days but when I go too many days eating grains or not watching my intake I feel like crap! Keep me posted on what’s working for you as you amp up training for the full!

      Liked by 1 person

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