Which is better: Training With High or Low Carbohydrate Stores?


By Chris Carmichael

Coaching is a push-and-pull between tradition and innovation, between “If it ain’t broke, don’t fix it!” and “Newer is better!”. During my coaching career I’ve been on both sides of that divide, always seeking innovation but wary that innovations that sound good don’t always lead to improved performance. Training when you’re low on carbohydrate (CHO) is getting a lot of attention right now, so let’s take a look at what it means for you.

The idea behind “Train Low” is to deliberately go out for a training session when you have partially-depleted CHO stores, when you’re low on CHO energy. But there are questions athletes need answers to:

Why Train Low?

The reason most cited for this approach is to increase an athlete’s reliance on fat for fuel, thereby forcing the body to improve its ability to burn fat for fuel. If you can burn a higher percentage of fat at all intensity levels your CHO stores will last longer during rides and competitions. That means you’d have more high-octane fuel (CHO) for high-power efforts when it counts. Sounds great!

How to Train Low?

There are a lot of ways to reduce carbohydrate availability during exercise, but the two that are most common are starting a workout without replenished CHO stores or not consuming carbohydrate during prolonged workouts. The first scenario can be achieved by exercising first-thing in the morning (before breakfast) or training twice in a day without replenishing CHO between workouts.

What happens when you Train Low?

Your power outputs during interval workouts will decline. A number of studies (including Yeo et al., 2008) have reported about an 8% decrease in power outputs during high-intensity intervals (5minute maximal efforts). When it comes to endurance rides you always slow down as the ride gets longer. With low CHO availability you will slow down sooner and more substantially. Your perceived exertion will be higher. Essentially, the end of a 3hr low CHO ride will feel like – and your muscles will be in a similar condition to – the end of a 5hr high CHO ride.

This somewhat logical consequence of training with low CHO availability has led to the idea of Train Low/Race High and subsequently Train Low/Train High methods where you do lower-intensity endurance rides with low CHO and prepare to perform interval workouts or race with high CHO availability.

But does it work?

Yes and no. For instance, Yeo in 2008 found that despite the lower power outputs during high-intensity intervals in a low CHO state, subjects experienced improvement in whole body fat oxidation and resting muscle glycogen storage.

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If you are going to Train Low studies (Akerstrom et al., 2009; De Bock et al., 2008) found that training without consuming CHO during workouts doesn’t enhance the adaptations we would normally see from those workouts. This suggests that a lack of CHO replenishment prior to a workout is a more effective way to Train Low than restricting CHO feedings during a workout.

The bigger problem is that while Train Low philosophy has positive impact at the cellular level it’s impact on real-world performance is less certain. In short, it improves performance for some athletes and not others, because in the real world you compete with your whole body and performance is also influenced by the cardiovascular, central nervous, and endocrine systems.

So, WHO is Train Low recommended for?

Intuitively, athletes think that the fittest riders are the ones that would benefit from new techniques like tweaking CHO availability. Pros who are already close to their maximum potential and are looking for tiny advantages can benefit from Train Low methods. In fact, they were doing it long before it was cool!

The other group that could benefit from Train Low is less obvious: time-crunched athletes. This group typically has 2-3 interval workouts a week and a longer weekend endurance ride. There may be some benefit – and no real harm – to completing this longer weekend ride before breakfast (low CHO availability) for a few weeks. Just know you won’t feel great, your perceived exertion will be higher, and you should take food with you (remember, low CHO stores seem to be more important than low blood sugar). I still recommend completing weekday interval workouts with high CHO availability, however. Experiment with one portion of your overall training plan and stick with proven workouts for the rest of it.

I don’t recommend Train Low for elite amateurs (Cat 1 and 2 in Elites and Masters). It’s not because it won’t work, but rather because it introduces a lot of risk. They already have a very high workload and train 5-6 times a week. There isn’t a lot of room for error and they haven’t reached the point where all the fundamental aspects of performance are already optimized (like the pros). Time-crunched athletes can get away with it because their training load and workout frequency are lower so they can better absorb and recover from the mistake. When elite amateurs make mistakes with how and when Train Low methods are utilized, it often does more damage and is harder to recover from.

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Comments 37

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  2. Just trying to make sure I understand as I consider myself to be a “time crunched athlete”.
    The article is suggesting that I do my short weekday workouts with High Carb Availability, but my longer weekend ride (when I’m most likely to bonk)with Low Carb Availability?
    Not sure I understand why I would want to train that way. One of my objectives is to lose weight while not passing out 😛
    Seems like I would want to do that the around?

    1. Lose weight while not passing out?
      Lose weight: Sustainable Calorie deficit.
      While not passing out: Put your CHO around your training.

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  7. What would a good level of Ketosis be, using urine strips? I am between small and trace. Is my body just producing what I need and can/should I try to get it higher. With salads and veggies I may be at the high end of carbs (50g). Because I work out 6 days a week can I go higher than 50?.


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  9. The CTS article is superb! The “Train Low” concept is not new. It started in the body building community and made its way into endurance sports many years ago and is more commonly known as FST or “Fasted State Training”. I don’t know where the words “Train Low” came from, whether that is a CTS term or from another source, but as described in the article, this is FST (although the article only focuses on carbs). I can’t use his name here, but I know one of the world pro MTBers (now retired) who used FST-training very effectively (and had monster FTP and endurance #s to show for it). What makes the CTS article so good is that, beyond explaining the basics of its purpose (as most FST articles do), it also describes its limits (what it is good for and not good for).

    The discussion of Ketosis, or any other nutrition plan, to improve body composition or possibly overall performance is only minimally related to the CTS article and perhaps better placed in other CTS-nutrition related articles.

  10. This is great advice for those looking to improve performance. One question is how often should one train this way? I know the answer depends on how many times a week you train and what level of athlete you are. Once a week? Every day?

    1. @Steve: The world pro MTBer I referred to in my response did it approximately bi-weekly.
      While his FST endurance rides (water only) were typically 5 hours, probably few of us on this forum have our bodies trained to do that. Since lots of other data suggests that our glycogen stores have sufficient energy to fuel us for about 90 minutes (for an endurance level ride), likely we will get the benefit riding at this level for an additional 60-90 minutes (2.5-3hr total ride). Anything longer without fueling with carbs+ and we will likely just be suffering with negative benefit (i.e. eating away at muscle for energy given the difficulty of converting fat without significant training to do so).

  11. Trying to research this and have only become more confused. I am an avid cyclist road and MTB. “Train” riding 4 +- days during week and extended did on weekend. I participate in mtb races and am looking g I to raci g road Crist. Be doing keto/LCHF ( for me 50 net carbs or less) for approx. 4 mos. which has helped me lose weight down to about 195. 185 is my goal and would make me very lean. It seems lately that after initial benefit in performance (possibly just from weight loss) it seems high intensity aspect may be suffering. Do i need to introduce extra carbs during training or racing in the form of gel or bars or will this kick me out of ketosis and add back weight and start from square one?

    1. If indeed you are keto adapted (you can get a monitor to test a small pinprick of blood from your finger – the type that type I diabetics use to test if they are in keto-acidosis). The problem once you take in a lot of CHO it throws you out of the keto adapted state. Also it has been demonstrated that a ketogenic diet can blunt your response to CHO when you do ingest it (hence poor performance during HIT). No increase in performance has been demonstrated from keto-adaptation – infact it has been shown to actually harm performance in some studies, although some of the methods were indeed flawed (not long enough to keto adapt and also this was not tested to see the level of keto adaptation). It has been shown to promote weight loss and increase lean body mass (as a % of total mass though). Current CHO guidelines advocate periodised CHO intake – train low etc as promoted in this article to increase oxidative capacity (increase in mitochondrial mass etc). Never the less currently no study has demonstrated improved performance with a periodised diet – although this may be due to the length of time it takes to see improvement (most studies are over 6-8 weeks).

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  15. Hello again,
    I posted a reply last year and raced the Imogene Pass. Ouray, Co. Over Imogene Pass 8,000ft- 13,100ft – 8,000ft. Telluride, Co. My findings were, I lost about 5% body fat (which made me happy) I did notice that I never really had the “get up and go” energy. However, while running through the the finish line, I felt like I could keep running for at least a few more hours. My time was about 40 minutes slower than normal, which was not what I had hoped for. My conclusion, I think it would be great for an ultra endurance race, but 17 miles (even though it’s considered a high country marathon) just wasn’t worth it. I think that next time I race, I would maybe train keto and race with carbs. Would love feedback.
    Terri Oliger

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  20. A lot of great stuff here. I’ve been lo carbing since January including going into ketosis for a month or so in Feb and March. So here are my results.
    A1C: I’m type 2 diabetic (no meds for 12 years), my A1C has been as high as 7.2. Last year it was 6.2 – got a 5.7 result in the last of February. Average fasting glucose levels have gone from 110 to 85. I’m still trying to determine what carb levels are good for me. I suspect its around 50 g per day.
    Cycling – I’m like the other post – old and slow, not a racer. I typically don’t fuel up before a ride. Its been great – plenty of energy! But I attended a CTS camp this month and found that I needed more carbs for climbing power. I agree that it’s probably more useful for the time crunched as opposed to the pros. The Volek and Phinney book is a good resource and I’m looking forward to more research in this area. Another book that helped me understand this is Keto Clarity.
    So, Chis this is a great and timely post and I’m looking forward to more on this topic.

  21. I have been doing research on a ketogenic diet for athletes. I decided to try and run the Imogene Pass Run (near Telluride) this September, 17.1 miles, keto adapted. I’m wondering if your research studies were with keto adapted athletes or not? I think one has to be keto adapted (2-6 week adaption, usually) in order to really know what the effects would be.

  22. Another approach, of which you may be aware, is the ketogenic diet for endurance cyclists and athletes. N.B. the research of Jeff Volek and Steve Phinney. After ketogenic conversion, these athletes burn mostly fat and need very few carbs and become “bonk proof”. Timothy Olson, winner and record setter in the Western States 100 in 2012, was such an athlete and needed very few carbs in 14+ hours of racing in 2012. Volek has specifically done research on cyclists on the ketogenic diet. His research indicated that power output and intensity for cyclists are, if anything, better on the ketogenic diet and since these cyclists are burning primarily the 20,000-40,000 calories of fat stores that any athlete carries (regardless of body fat percentage) — they are essentially “bonk proof.” I’d be interested to know if you’ve read this research. My wife, a cardiologist, has read the research and says it makes complete scientific sense. We are both cyclists who have been on the ketogenic diet. We find we need virtually no carbs on 3-6 hour intense rides. Of course we are not racers! But we would be interested in your comments. Best regards – Moss Patashnik, Seattle, WA

    1. This prompted me to do a bit of research on Ketogenic diets & stumbled upon Anthony Colpo’s site. He followed various low carb, ketogenic diets for several years but after getting dropped on a ride did he start adding carbs back to his diet. He provides many references on his opinions of low carb diets on athletic performance. A particularly interesting & amusing one at that is his reply to Danny Albers who attacked his claims on his blog.

      anthonycolpo.com / sorry-danny-albers-but-low-carb-diets-still-suck-for-athletes/

      He also references Timothy Olson’s intake of carbs during his race.

      1. Here’s the link to his response to Phinney’s claim that Tim Olson was on a low carb diet.


    2. Well, such a wide variety of posts and results on Keto. I have been lo carb/keto for 3 months. May have rolled out of ketosis for a week around easter 🙂 It seems I have become bonk proof, but my power has been lacking. In retrospect, my sleep has been suffering as I watch the road to Lord Stanley (Cup). When I get a good sleep and am rested, I do well. I ride about 220-250miles / week. Long rides on Saturday (hills) and Monday (flats). I swim 2 x (3 -4 miles total) a week with masters group, so Monday and Wednesday are double workouts. My swimming seems to be suffering most. So I was powering out at first, I lost about 17 -20 lbs from 178 to 158lbs. In general my week rides are early monring rides up arouond 4am and on bike from 4:30/45 to 6 :45/7. About 20 miles with a pack avg speed is 23 to 27+.
      Overall, I’d say I’m not as powerful as I was at 175-8. But my allergies are much better, asthma is improved and I have been using less OTC prostrate supplements. I’m much more present and my mind is more clear. I do at least 1 24 hr fast a week. I am a no food before workout guy, can’t do it. So the intermittent fasting isn’t difficult with at least 16 – 18 hrs. I don’t want to get below 150 so I have increased my food intake, more salad and veggies, to counter the weight loss. I’m 69 y/o, have always worked out.
      I would agree that I haven’t gained power, but I am holding my own on the long climbs and false flats, chich always gave me trouble before (maybe weight loss).
      I’m a believer in the Lord Jesus Christ.

  23. I had not heard the “train low” terminology until today, but experimented with this method on a hunch last year to prepare for a mountain bike ultra-endurance event. It was my third such event, and this approach was a great success. While lower CHO certainly reduces my peak output (and will have a cumulative negative effect on my speed if I always train that way) during events where it is impossible to store or eat enough CHO to last the duration, I tend not to hit the wall if I have been “training low.”

    1. Post

      The idea is less about burning more fat during the individual ride you’re on, and more about getting your muscles to a CHO-depleted state sooner during a ride (an hour into a 2-3 hour ride instead of 3 hours into a 5 hour ride) so your body adapts the way it prioritizes and uses fuels. Over time, the idea is that you’ll train your body to burn a higher percentage of fat at moderate and high intensities, thereby sparing glycogen (your high-intensity fuel source) for when you need it most. During an individual ride, you’ll burn a higher percentage of fat once glycogen stores are depleted, but you’ll also be going slower and burning less overall energy, so the absolute number of fat calories burned may not increase much or at all. – Jim Rutberg, CTS Pro Coach

  24. Will training low lower my Hemoglobin a1c reading? Three months ago my a1c was 6.2% and last week it was 6.1%. Would training four to six times a week (I don’t like to train much in wet weather) be likely to reduce it to less that 6.0%?

    I am not interested in “going faster” (a lot of people are already faster, and even with substantial increase in my riding speed, they will still be faster. I’d rather be a healthier rider.)

    1. A1c is reflection of your blood glucose levels over time. In other words if you have higher blood glucose levels consistently over 3-6 months you will have a higher A1C. If your glucose levels are maintained in a more normal range then your A1C will also be normal. Stored CHO in the form of glycogen should not affect A1C. What may affect A1C though is that as you train your body to replenish glycogen stores as rapidly as possible you will keep your blood glucose closer to normal which will lower A1C over time.

  25. I am one of those time crunched athletes and one of the major missing links in my regimen has always been nutrition advice. Thus is hugely beneficial. Thanks.

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