Low Carbohydrate Training

I’ve been running here in Colorado’s San Juan Mountains for three weeks. Most of my runs have been low-intensity hike up/run down efforts lasting from two and a half to five hours. I’ve consumed calories during only two runs – a cup of veggie broth while pacing at Hardrock and roughly ten gels as well as a good deal of sports drink during the Kendall Mountain Marathon. A small part of the reason behind this was to shed a couple extra ounces here and there before UTMB, but the main reason behind the move was to work on my body’s ability to utilize fat as an energy source during the same race. While this ability would greatly benefit me during any long ultra, it’ll be even more important at UTMB where I’ll only have one spot halfway through the race where I can restock my gels, which are normally the vast majority of my in-race calories.

Although much recent training advice has been toward runners fueling throughout their long training bouts, this sort of low-to-no carb training isn’t without precedent. I’m sure many ultrarunners and other endurance athletes have done this by default. I’ve much enjoyed this low-carb training article from First Endurance when I read it a few years ago and again now for its presentation of research on low-intensity, low-carb training.

While I’ve not been engaging in the practice, the article suggests not replenishing glycogen stores via carbohydrate consumption prior to some of these low-intensity, low-or-no card training sessions. Years ago, I heard of some top New England ultrarunners (if I remember correctly, Todd Walker and, maybe, Leigh Schmitt) occasionally running back-to-back “bonk runs” on the weekend in which they’d go long at a moderate-to-hard effort on Saturday with no carb intake, refraining from refueling with carbs afterward, and then running moderately long again on Sunday in an already glycogen-deleted state.

I will continue to ingest carbs, usually as GU energy gels, during races (I ate 30+ GUs during Western States) and higher intensity long runs. I’ll also continue to bring carb sources with me during all of my long runs as an emergency backup. However, I’ve enjoyed my no fueling experimentation this month as well as my low-carb long run training throughout this spring and summer. I think it’s too early to tell if it’ll result in a major performance boost on race day, but I don’t feel like my low-carb training plan has hampered me in the least the past few weeks.

Call for Comments
Do you always fuel during your long training runs? Do you ever restrict your carb intake during training runs? Do you routinely use such a restriction?

It’d be great to hear your reasons for whatever level of carbs you use during training.

There are 58 comments

  1. Chris

    I switched from eating high-carb (followed a complex carb eating plan by top nutritionists for athletes) to eating low-carb, and I found Volek/Phinney's book: The Art and Science of Low Carbohydrate Performance — http://www.amazon.com/The-Art-Science-Carbohydrat… to work really well for me. For me, that means <=50 grams of carbs per day. I test my bohb levels and they are right in the right range for being fully keno adapted. It's a myth that high-carb is the "only" way for long-distance running. A friend of mine who has been fully low-carb/keno adapted just completed a 50 mile trail race (finished in the top 8 I think) and is getting ready to run his first 100 mile strictly low-carb. According to Phinney/Volek, the ability for the body to use fat as the primary energy source is tied to the amount of carbs ingested, when they go up, the ability to utilize fat can quickly go down. I'm sure everyone's body reacts differently, hence why I test my blood bohb levels to ensure I'm in the right zone. That said, I've only been running for 1 year, have only run 2 half marathons and am going to attempt my first marathon in a few months. I have found I have much more energy and less fatigue in my long runs (only 14-16 miles so far — i know, not far given this website) once I became keno-adapted versus my prior high-carb.

    All that said, I don't believe low-carb is the "only" way to go, just that it's a viable option and there is a ton of science behind it when you really study the history (which Volek/Phinney do a fabulous job at) and carefully implement it, track every single carb you consume down to the minute amount, so you know exactly at the end of the day how many carbs you consume, etc.

    I've benefitted also from losing weight, not getting the shakes/tired/lows that you sometimes get, etc. I can go out and run 8-10 miles on an empty stomach, no fatigue, and I'm not hungry afterwards and may eat 2-3 hours after a run, with no shakiness, etc., because I consume the majority of my diet from fats and moderate protein.

  2. Laura

    Hey, just have a quick question. I am on day 9 of low carbing, and am finding running VERY hard! I used to do a 7mile trail training run everyday & now I can't even do half that without stopping!! Is this normal? Please tell me it'll get better soon as I love running & if I don't start to enjoy it again soon I'll have to quit this way of life! Any advice gratefully received.

    1. George T

      Yes, it is normal. It took me two weeks with some bad runs to get adjusted. It took my wife an entire month. Not only it gets better, it gets a lot better (running gets a lot more enjoyable)

      1. Laura

        Thank you!!!! That's exactly what I wanted to hear!!! Do you think if I had a gel just before running at the moment it would help? I don't want to undo any good I've done but I am itching to get out there!! I really appreciate you responding

        1. George T

          I think you should stick with your low carb diet. Eating gels will just delay your adjustment. There are a few suggestions recommended to speed up the adjustment: 1) Eat more fat. 2) Get some extra salt (like a broth) before exercise.

  3. Allan Holtz

    I would NOT low carb. I do not think it is conducive to a high run lifestyle. I would just be careful regarding the nature of the "carbs" I ate, i.e. I would go light on the pastries, pastas and desserts and heavy on the whole grains, fruit and vegetables.

    Happy living,

    Allan Holtz

    1. George T

      Have you tried it? In my 2 years of eating low-carb I have completed 2×100 mile races, 3×50 mile races and about 15x50Ks, all with excellent results. I have more energy than ever, especially towards the end of the race. I can run a 50K without any food. I have never hit the wall. Works great for me.

  4. Allan Holtz

    I do consume home made gel during marathon to 100-mile races to fuel those (long) efforts. But that is the only time I use them. In a blender I blend 475 grams of maltodextrin (Maltrin M180) with 25 grams of soy protein (protein optional) with a heaping teaspoon of cinnamon powder with the contents of 5 Succeed S-Caps and 300 grams of water. This creates 800 grams (2000 calories) of gel (about 7/8 quart of gel). I consume about 200 calories every 15 minutes of long races.

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