Eat (some) carbohydrates if you wish to compete fast and far…

Eat (some) carbohydrates if you wish to compete fast and far…

The carbohydrate conundrum? I didn’t realise there was one 🙂

(please see the footnote for an article that came under my nose today a day after writing this).

This is a post inspired from the ISSN (International Society of Sports Nutrition) forum that I am compelled to share as it speaks LOUDLY about why the ingestion of carbohydrates is crucial during high-end endurance training and in competition.

Two strategies that I practice with my triathlon and endurance athlete clients is flexible carbohydrate periodization with their training regimen and elevated carbohydrate intake for competition day….

Why? Because for most athletes these strategies work. Period.

case closed 3

The secret is to work with each unique individual taking their metabolism into account as there (seems to be) variance between athletes regarding optimal carbohydrate intake on a daily training basis.

So for athlete X, for example, we may use a moderate carbohydrate intake on most training days. And then switch this around with specific training sessions lower and other sessions  higher in carbohydrate intake (such as very intense and long duration sessions or double training session days).


For example a hard track session in the PM following an AM aerobic bike or aerobic run may require a higher volume of carbs in between sessions to ensure recovery from session A for a quality session B.

Or on the flip side athlete Y may fare well on a lower daily carbohydrate intake in general, and then we may do some (aerobic) sessions lower again with pre-training fuelling only from protein and fats or fasted and then on other days we may raise the carbohydrates from low-moderate to high-moderate to ensure optimal fuelling and recovery for the sessions specific to this day.

Athlete Z may be different again and do (some) morning sessions following a light breakfast that is mostly protein and fats (ie low in blood glucose) and then in the evening reload glycogen by consuming a meal containing carbohydrates. However this athlete will have to eat ample carbohydrates for longer duration (e.g. aerobic 2-4 hours bike sessions) or more intense sessions (such as time-trial bike sessions or fartlek running sessions).

All athletes that practice flexible carbohydrate periodization that tend towards lower in glycogen levels in day to day training are recommended to have key re-feeding days every week to prevent staleness or the risk of over-reaching and to ensure that specific sessions are done glycogen replete so as to safe-guard training adaptations. Pushing the number of low glycogen training sessions completed each week  too far (i.e. more than 2 to 3 for well-trained athletes) can have consequences on the HPA (hypothalamic-pituitary-adrenal) axis and cortisol, DHEA and insulin homeostasis; in addition to resulting in reduced training quality, hampered training performance and poor recovery never mind falling ill due to a compromised immune system.

Furthermore failing to identify the sessions requirements correctly can lead to bonking within the session and potentially a whole load of DOMS woes (delayed onset muscle soreness), in addition to feeling weak, having reduced power and poor muscle strength in subsequent sessions.

low carb
low carb
contains carbs
contains carbs

Competition day eating: As a rule all athletes are recommended to raise their carbohydrate intake in preparation for competition and on competition day.

“In other words after months of practicing variable and in general low to moderate carbohydrate intake race preparation and race day involves ample carbohydrate intake and a degree of eating your way around the course :-)”

Contrary to what most people believe recovery is protein focused unless you have a hard session the following day when recovery carbs will be recommended (more often than not you don’t need more once the race is put to bed).

eating on the bike

Yellow jersey Alberto Contador (Discovery Channel/Usa) (L) and his US teammate Levi Leipheimer eat a banana while riding during the 18th stage of the 94th Tour de France cycling race between Cahors and Angouleme, 27 July 2007. AFP PHOTO / FRANCK FIFE (Photo credit should read FRANCK FIFE/AFP/Getty Images)

There is (thus far) an insufficiency of research to document competing to a high level in endurance events in a ketogenic or glycogen deficient state. If you want to compete on race day at an intensity that brings you close to and often beyond that line of anaerobic threshold, then blood glucose levels must be maintained to support performance.

If you wish to optimise positive adaptations to training then strategic inclusion of carbohydrates in a nutrient dense diet constructed around ample protein, fats, and vegetables is recommended.

However as always there will be anecdotal stories to the contrary such as the recent journey of Rob Verkerk and also discussions as here; and then back to the Kenyan’s diet and here is a nice infographic; thank you Yann Le Meur:

professional cyclists

Opinion tug-of-war

There are opinions everywhere in this gig; and so many google experts say to “go keto” and that “low carb/ no carb” is what endurance athletes should do. If you are happy with intensities sub 65% HR then by all means fire ahead (and if you are willing to do an experiment of one that may or may not aid your performance).

Yes the body can work off beta oxidation of fats at lesser HR intensities and this will work fine if you aim to finish. If your goal is a fast race; then from all that I have studied I don’t recommend a ketogenic or low carb diet.

Coming from a low carb diet background myself I so wanted to believe that training and competing at a high intensity and volume was possible while remaining low carb; I have found that it is not so :-(.

Even for myself I have had to bite the carb bullet now that I am training for half ironman and move things around in my diet.


There is too much research in favour of maintaining carbohydrates in the diet when training to a high level in the word of endurance sports to be ignored.

I have read the research to death and found that a keto or low carb diet  for most simply is not possible to sustain and NOT linked with performance or health benefits in the long-term.

Initially some people may see performance benefits; often this is due to the removal of carb junk from the diet and/ or the initial weight loss with body comp improvements (a low-carb high-protein moderate-fat diet is superb for weight loss and improved body composition). However in the longer term and when training at intensity and for multiple hours in every week you may be wreaking havoc on your health, hormones, (fertility), cognitive function & mood, and ability to continue training to a high level.

The Low carb Vs High carbohydrate and Low fat Vs High fat diet for endurance sport is hotly debated online and in many a science and non-science based forum.  It is a veritable nightmare to navigate for the non-science trained person as misquoted science and pseudoscience can confuse and mislead.

As my ever practical boyfriend always says “look at what the pros are doing”.

  • Has anyone won the Tour De France following a low carb diet?
    Um not that I know of; try eating this many carb calories
  • Do the Kenyan runners eat carbs? Yes; lots!
  • Do most (if not all) top marathon finishers eat carbohydrates and use sources of glucose while competing? Yep.
  • What are the best pro triathletes and cyclists doing? Eating carbs…
  • Have you seen any pro and world-class age group athlete intentionally not taking carbs on board during a race? Not me!
  • Are any of the above athletes fat from eating carbohydrates? Um definitely not…
  • Chrissie Wellington is a nice example of a balanced attitude to everything that she does. Here she is on food; and well it would be remiss of me to not add this stellar instalment from her.
  • On a side note you may find this article interesting as cardio has been bashed lately also as a reason for being fat…. honestly!! Follow the links in the article as they are worth a read. I love Jose; a scientist that knows enough to write with humour!

Take home message – ask questions, read the research, and watch what the best are doing….Then find your own “best zone” regarding food and specifically carbohydrates (the same goes for fluids). Don’t be afraid to try a few different approaches in the off-season.

So here is an excerpt and some abstracts that will help ease your mind about the whole carbohydrate conundrum.

Let me be clear here also. Although I am writing this article to explain that carbs are not the anti-Christ of endurance training I do also believe that we need less (carbohydrates) than we are in general told, and that we should not only choose them wisely but time them wisely.

Better options are root vegetables such as sweet potato, potato, squashes, beets and parsnips; non-gluten containing whole-grains such as rice, millet, quinoa, buckwheat, and gf oats; fruits and dried fruits. Vegetables are in general a free for all.

healthy carbs

Finally quality protein and fats are an essential in the diet of the hard training endurance athlete.

Credit to the ISSN for this post and the lovely Chad who drew my attention to the research linked below:



Carbs> Fat loading…..

Rob Krar has now won two of the most iconic 100-mile races in North America winning both the Leadville 100 Colorado and the prestigious Western States Endurance Run 100 miler which he has won twice (2014, 2015).


Rob Krar trail running on the South Kaibab Trail. Grand Canyon National Park, USA
Rob Krar trail running on the South Kaibab Trail. Grand Canyon National Park, USA

In his most recent win the 38 yr old had the second fastest time in the events 31 year history. Part of this success he attributes to helping his body better utilize carbohydrates. Looking back to 2014 when Rob agreed to participate in a research study of elite ultra-marathoners……”Anecdotal claims suggest that an increasing number of ultra-marathoners purposely undertake chronic low-carbohydrate (CHO) / ketogenic diets while training, and race with very low CHO intakes, as a way to maximize fat oxidation and improve performance. However, very little empirical evidence exists on specific fuelling strategies that elite ultra-marathoners undertake to maximize race performance.

Three world-class veteran male ultra-runners (mean±SD; age 35±2y; mass 59.5±1.7kg; 16.7±2.5h 100-mile best-times) agreed to complete a competition-specific nutrition intake questionnaire.

Throughout 2014, the athletes competed in 16 ultramarathons with a total of eight wins, including winning the prestigious Western States Endurance Run 100-miler (14.9h).

The average pre-race breakfast contained 70±16, 29±20 and 21±8g of CHO, protein and fat, respectively. Throughout 100-mile races, athletes consumed an average of 1162±250g of CHO (71±20g/h), with minor fat and protein intakes. This resulted in caloric intakes totalling 5530±1673 kcals (333±105 kcals/h). Athletes also reported consuming 912±322mg of caffeine and 6.9±2.4g of sodium. Overall, commercial products accounted for 93±12% of energy intake. In conclusion, these world-class ultra-runners practice fuelling strategies that maximize CHO intake. Despite having limited professional nutritional input into their fueling approaches, all athletes’ individual intakes for CHO and sodium are congruent with contemporary evidence-based recommendations”

This type of strategy is something that is often found in elite endurance athletes who are training to maximize carbohydrate intake as a fuelling strategy on race day by adding in 2 – 4 low-carb training sessions a week during preparation. In 2012 the Canadian Sports Center used a 16 week carbohydrate fuelling protocol with 3 elite marathoners to prepare for a race. The athletes averaged ~13 training sessions per week for a total average training volume of 182 km/wk and peak volume of 231 km/wk, during this time the runners averaged 2.5 ± 2.3 low-CHO-availability training bouts per week. Two of the marathoners achieved personal bests (2:11:23, 2:12:39)…..

“The athletes kept detailed training logs on training volume, pace, and subjective ratings of perceived exertion (RPE) for each training session over 16 wk before race day. Training impulse/load calculations (TRIMP; min Ă— RPE = load [arbitrary units; AU]) and 2 central nutritional techniques were implemented: periodic low-CHO-availability training and individualized CHO- and fluid-intake assessments.

Athletes averaged ~13 training sessions per week for a total average training volume of 182 km/wk and peak volume of 231 km/wk. Weekly TRIMP peaked at 4,437 AU (Wk 9), with a low of 1,887 AU (Wk 16) and an average of 3,082 ± 646 AU.

Of the 606 total training sessions, ~74%, 11%, and 15% were completed at an intensity in Zone 1 (very easy to somewhat hard), Zone 2 (at lactate threshold) and Zone 3 (very hard to maximal), respectively. There were 2.5 ± 2.3 low-CHO-availability training bouts per week. On race day athletes consumed 61 ± 15 g CHO in 604 ± 156 ml/hr (10.1% ± 0.3% CHO solution) in the following format: ~15 g CHO in ~150 ml every ~15 min of racing. Their resultant marathon times were 2:11:23, 2:12:39 (both personal bests), and 2:16:17 (a marathon debut). Taken together, these periodized training and nutrition approaches were successfully applied to elite marathoners in training and competition”

I hope this post has been helpful to you,

Love, Andrea

PS my inspiration Mirinda Carfrea; a pocket rocket.



A day after writing this article my attention was drawn to this very interesting article. And a few days after another and then a few days on and another… it seems people like nothing more than a good debate. I am linking them all for you to have a gander.

I highly recommend that you read the articles in full and including the comments and then come back to my thoughts here.

I think there are many fascinating Qs that we are seeking As for in relation to the Carb Vs. Fat debate…I think in summary: there is a continuum of athletes that require a spectrum of macronutrients for optimal health and performance.


Something that is consistently on my mind of late is that athletes aren’t a “one size fits all” in their nutrition requirements. I believe that there is a spectrum of optimal macronutrient ratios and an “ideal dietary performance enhancement zone” (for want of better words) for each individual and it is up to a well-trained nutritional therapist, coach, and sports dietician to find the best fit for each athlete.

I believe that there is a continuous spectrum of optimal intakes from carbohydrates, protein, and fats and that perhaps factors such as pre-natal nutrition, epigenetics, genetics, race and culture, country of origin, ancestral diet etc. play a role (we can even go so far as to say belief systems will have an impact too as I firmly believe will!).

I don’t know the answers on this one and I am hoping that the Carbs Vs. Fat brigade start to invest their energy of warfare from against one another to working with one another to answer questions about why some athletes do better on carbs, others on fats and the majority somewhere in the middle. Will we be able to better know whom can fat adapt? Which athletes do better on training low and competing high, do some athletes fat adapt on lower carb intake (versus none); will periodization of carbs and nutrient timing work for some such that there will be some carbs in certain identified meals during the week?

And what about women and the impact of hormones on insulin homeostasis; there may be times in the menstrual cycle when low carb is a no-no due to enhanced insulin sensitivity raising the risk of hypoglycaemia. We also suspect that there may be times during the menstrual cycle when fat adaptation is augmented in response to a low carb diet and when carb loading is more successful and also distinct hormonal patterns making training adaptation most likely. Here is a paper that explores some of these ideas: The effect of the menstrual cycle on exercise metabolism: implications for exercise performance in eumenorrhoeic women. 

Furthermore, I have been doing a lot of research of late into over-reaching, non-functional over-reaching, and over-training syndrome (yes…. science loves definitions). And although the glycogen theory is a very weak explanation for many of the symptoms and connecting these all up, it does provoke me to advise that we should be watching out for athletes susceptible to bonking (hypoglycaemia), as repeated instances may be linked with the development of chronic “tiredness” when the brain starts to protect the body by slowing everything down (fatigue).

Does periodization of nutrition with the training micro-cycle best protect the health, fitness, and performance of the athlete training for 7-10 hours plus each week. And when this is achieved can we then progress to assessing the potential of the athlete to train ‘lower’ and compete ‘higher’.

One thing that is consistent regarding every athletes needs is that protein should be of good quality and varied (red and white meats, organ and game meats, fish, shellfish, vegetarian sources), fats fresh and of good quality (mostly pre-formed omega 3 from fish, quality dairy and meat fats, monounsaturated fats, coconut fats, nuts and seeds; and minimal processed oils) and carbohydrates mostly from root vegetables, vegetables, and fruits with minimal gluten-free grains on an as needed basis.

One thing that did stand out to me about the closing note in the article discussing Bevan’s experience and this was that his blood lipids were above normal previous to his low carb high fat diet (and resolved since). This would make me wonder does he have a tendency to insulin (sensitivity) issues and metabolic syndrome and that he is a metabolic type that will do better with less carbs  in his diet. Just as many with insulin problems will fare better on a Banting diet. This is not most “normal” athletes.


Here is a nice article discussing the diet of Tim Reed, pro-triathlete: Elite Fuelling Tim Reed. This article demonstrates what I would consider a more or less balanced and healthy athlete’s diet. It is NOT however a low carbohydrate diet or one that falls within the macronutrient ratios that he mentions in the article (I don’t know how he came to describe it thus!). If anything, however, this diet is a little too high in protein for an endurance athlete for my liking. Readers of this blog may find the article interesting.


This is the final article that came under my nose and it discusses “Which diet is better for cyclists? High-fat or high-carb” I agree with most comments here apart from the comment concerning fat metabolism when on a high fat diet (see the section titled Burning Fat Doesn’t Mean Burning Body Fat).

I believe that some (steady state aerobic) sessions done using a lower in carbohydrate intake with moderate intake of fats and protein or indeed completely fasted with a low-blood glucose level are helpful in the experienced endurance athlete to further promote metabolic adaptations  to enhancing fatty acid mobilisation and oxidation thus improving endurance economy at sub threshold intensities (best supervised with the guidance of a nutritional therapist experienced in sports nutrition). However not all of the fats oxidised for these sessions come from diet; we do contrary to the claim in this article, mobilise and metabolise fatty acids from endogenous stores. Here is a nice article should you like to learn more: Lipid metabolism during endurance exercise 1,2,3. and also here: Regulation and limitations to fatty acid oxidation during exercise.


I hope that all the above notes give you some pause for thought; as ever it is not a straight forward issue when it comes to fuelling! I especially like the comment in the Which diet is better for cyclists? High-fat or high-carb” article reminding you that the basics are always the best place to start before tweaking the specifics.


Please do add your experience and thoughts being cognizant of the fact that every athlete is unique.

x Andrea

This Post Has 2 Comments

  1. Good stuff thanks to referring to my article on my blog re IRONMAN. I agree that there is a carb continuum. We need to take into account the athlete’s age, health goals, performance goals (these can go opposite ways especially for non-pro athletes ) where lots of carb fuelled training and raining isn’t necessarily that great for your metabolic health probably too many ROS and oxidative stress etc.

    There’s no doubt that for ultra endurance its better to be abel to oxidise fat at a higher rate as we see in veto athletes. As you move down to just endurance, then if you want speed then you need carbs and the mix between carbs and fat burning predicts performance. Exactly how you know this is still trial and error even in our labs with all the best gear the individual repossess are so different.


    1. Hi Professor Schofield I am super stoked to hear back from you many thanks for adding your comments here. I think that this demonstrates to readers that most researchers and persons working in this field have a burning passion for sharing knowledge and working with one another. This is vastly different to my experiences within the medical profession (coming from a pharmacy background) also I am often laughed at my pharmacist colleagues for shunning pharmacy and taking my education and career into the world of health, nutrition and fitness. I believed I would make a difference to peoples health at the naĂŻve age of 18 when I started my pharmacy degree it didn’t take too long staring at a shelf of statins, antidepressants and mood altering medications to see that this most certainly was not the solution for peoples health so I did a career change. I never regret my pharmacy training however as it gave me an analytical mind…. it did take a few years to open my mind all the same but I guess an ability to accept that you know far les than you think you know comes with age. I think i leapt a fair bit out of the conditioned box a few years ago!!

      We will always seek to have answers about what we are seeing in our athletes, from an amateur to pro level; what makes the best better and what hampers us normal hard training joe soaps? Also how can we more simply identify the carb sensitive from the carb tolerant. I feel that examination of fasting blood fats and body fat % and distribution can give some clues. I agree with you regarding a general belief in the over use of carbohydrates and wish that the sports dietician and sports med guidelines would update their recommendations as I am fed up of seeing Gatorade beside the treadmill and the excessive consumption of carbs in the endurance world (and perhaps too few in the figure fitness and strength world)… the world loves dichotomy 🙂 and the sports nutrition industry loves it even more!

      Keep up your hard work and excellent blog. Folks jump over here to Prof Schofield’s blog page here

      Thanks again Grant; Andrea (a fellow fat food fan 🙂 )

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