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Apr 23, 2013 04:51 PM

Any low-carbing distance runners here?

Just curious if anyone else here successfully stuck to a low carb diet while doing longer-distance runs several times a week? I'm doing fine with low carb for my usual 5-10km distances 3-4 times a week, but just signed up for my first half-marathon (end of Sept) and kind of wondering if the low carb plan may present problems with low energy. I'm doing the Slow Carb Diet where you are allowed meat, veg and legumes but no dairy products, and one cheat day per week which I generally schedule the day before my longest run so that I have extra carbs in my system. I'd be interested to hear about others' experiences.

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  1. I'm interested in your post (so thanks!) and will be following.

    Long-time distance runner (several marathons and ultras) who recently became "short-gut". So... new challenges for me. I can "do" dairy...but it doesn't "stick" long with me (so neg. source of energy/calories). Recent convert to the joys of salmon and avocado.

    Hoping to run a marathon this fall. Possibly interesting tidbits/inspiration/pitfalls for you and others. Mostly hope to pick up tips and learn via personal stories here.

    1. I remembered such studies/papers from my early days of learning low carb:

      Ketogenic diets and physical performance

      It seems to me that if you rely on carbs for fuel, you're at a higher risk of running out or low, whereas if you're in consistent fat burning mode, you have more than adequate stores that last longer.

      After adaptation, and with attention to the issues mentioned in the article.

      I should mention that my husband, no marathoner, still can run 6 hard miles on the treadmill, including on incline, on a very low carb diet after doing some weight training first. He sweats buckets and needs some Morton blended lite salt before and after, is all, or a V-8.

      1. I've been VLC for years and never had a problem bonking during long runs. As long as your total calorie intake is sufficient, you don't need carbs for energy once your body adapts to using fat and *dietary* protein (not your own muscle!) as fuel. In fact, your energy levels will be more steady and sustained instead of riding the carb roller coaster. If you're eating legumes, you're getting starchy carbs anyway.

        It may take a week or two to adjust, so don't get discouraged or freaked out if at first you're feeling more tired or weak. You'll adjust. If you find that you REALLY can't hack it without carbs, add a serving of sweet potato or other tubers here & there.

        1 Reply
        1. re: goodhealthgourmet

          The point about protein is a really good one, since it converts at a rate of about 58% to glucose, over hours, not rapidly the way carb meals do.

          I know that some ketogenic athletes will sip some dextrose in water or eat a few glucose tabs during a workout, just enough to fuel the immediate activity, and not enough to knock them out of ketosis, too. This way, they don't end up depending on glycogen stores at any time.

        2. Thanks for these very interesting replies, especially mcf for the link to the study about indigenous diets in the arctic. Fascinating stuff! I feel encouraged.

          1. Stephen Phinney, author of the article mcf linked, is co-author of a book called The Art and Science of Low Carbohydrate Performance, which is all about your questions. Another good resource is a website called The Eating Academy, maintained by a guy who is an avid self-experimenter, a dedicated low-carbohydrate eater, and a serious athlete.


            My answer to your questions from my own experience as an endurance athlete is that a low-carb diet can only improve your ability to complete longer distances, by improving your ability to draw on your stored body fat for fuel. Where you can run into issues is not in doing longer and longer events, but in trying to do them at higher intensities. It's one thing to run a half-marathon or marathon, staying always just at or below your aerobic threshold; it's quite another to race it. Assuming you are well adapted to use body fat, you can run or swim or ride at a modest intensity for hours and not burn through as much muscle glycogen as you would use for a 30-minute race.

            If you are running to win, not just to finish, you may find that a "train low[-carb], race high[-carb]" strategy works best. A book called The Paleo Diet for Athletes gives advice about this strategy, although IMO it suggests far heavier reliance on simple sugars and highly processed food than I think is healthy (or palatable).

            2 Replies
            1. re: ourswimmer

              Also, The Ketogenic Diet, by Lyle McDonald describes cyclical and targeted ketogenic diets to suppport activities and training.

              1. re: ourswimmer

                Thanks, this is interesting & I'll check out the resources you recommended. My intensity level is pretty low (I've yet to run 10k in under an hour, for example) so it sounds like based on your experience I should be OK for training to run longer events at a similar pace.