Nutrition, Podcast, Science

High carbohydrate, low carbohydrate, or periodised carbohydrate intake with Louise Burke, PhD | EP#236

 June 1, 2020

By  Mikael Eriksson

LISTEN TO THE EPISODE HERE:

In this Episode you'll learn about:

  • The "Supernova" studies - comparing the effects of low-carbohydrate, high-carbohydrate and periodised carbohydrate intake on endurance performance
  • How quickly does it take to get fat-adapted?
  • The impact of fat adaptation on fat oxidation and performance
  • Why a constant high-carbohydrate diet outperformed the more sophisticated periodised carbohydrate diet

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Shownotes

Background

04:35 - 

  • I am a sports dietitian at the Australian institute of sports, my current position is ”chief of nutrition strategy”.

    I have been working at the Australian institute of sports for 30 years where I have both been involved in research as well as applying the science.

The Supernova study

06:47 -

  • The study is quite unique since the study group comprised of around 30 top international race walkers that were all at the same training camp, making it possible to very carefully control their trading and diet.
  • The study investigated different approaches to using carbohydrates in training and racing including periodizing carbohydrate intake.
  • We found that high carbohydrate availability was integral to performance.

    Probably, it is also beneficial to have a high level of carbohydrates while training, especially for high intensity sessions.

    This can also be explained physiologically, as utilizing fat as a fuel requires more oxygen compared to when carbohydrate is used.

    The group that had a periodized carbohydrate intake during training (but not when racing) developed equally well as the group that had a constant high carbohydrate intake.

    The group with a low carbohydrate intake (both during training and racing) did not perform equally well as the other two study groups and this result has ben reproduced multiple times.
  • The race distance to evaluate performance was a 10 000m walking racing with a finish time of around 40 mins, hence, it was not a glycogen limiting distance.
  • In a follow up study we investigated the performance in a 20 000m walking race performed three weeks after a ketogenic diet had been finished, but once again, we did not see any benefits to train with a low carbohydrate intake in the training block leading up to the race (actually we did see a slight impairment in performance).
  • However, research has shown that a low carbohydrate availability could enforce the aerobic training effect.

    Therefore, we are theorizing that these elite athletes, despite what they ate, did have a fairly low carbohydrate availability due to their extremely high volume of training.

    Limiting the carbohydrate stores further did not create any additional adaptations.

Energy availability

24:10 -

  • We are currently conducting another study, which unfortunately is not finished yet due to the Corona situation and other obstacles that we have been encountered.

    However, in the study we are examining how performance as well as hormone levels and other health aspects are affected by energy availability in general and different energy sources.

    The different groups we are studying are one group that have a low overall energy availability from all sources (fat and carbohydrates), one group that get a low energy availability solely from carbohydrates while the overall calorie expenditure and intake is in balance and finally one group that has a constant high energy availability mainly from carbohydrates.

    The aim is to see wether energy deficiency states only can be attributed to a general low availability of energy or if the composition of energy sources available play an important role in the development of energy deficiency conditions.
  • Unfortunately, I do not have any results to share yet, however, during some pre study tests, we could demonstrate that the body’s ability to burn fat as a fuel can very quickly be trained to quite high levels.

    This speaks for that the intervention time of three weeks of the Supernova studies is sufficient to generate the kind of response to a ketogenic diet that we are targeting, which has been one of the major criticism of the studies (too short intervention time)

Consensus in regards to carbohydrate availability within the research community

30:30 -

  • It is fairly difficult to summarize where we stand knowledge wise today in terms of how an athlete should approach his or hers carbohydrate intake.

    There aren’t that many high quality studies done on the subject and most of them have had an intervention time of 3-4 weeks of ketogenic diet and during this time it is certain that major metabolic adaptions do occur.

    However, only a few longer studies have been conducted and the results from them are somewhat hard to interpret.
  • In the end I think that every athlete needs to consider the targeted event and analyze what kind of energy requirements there is and at what intensity levels you aim to perform as well as the availability of carbohydrate during the race and adept the training and nutrition to these demands.

Carbohydrate periodization

37:35 -

  • When it comes to if I would recommend for an athlete to implement a periodized intake of carbohydrates, I would say that it massively depends on the level at where the athlete is at.

    An elite athlete with a high training volume will automatically be low on carbohydrates during some sessions and will hence get the desired effect from low carb training, while a recreational athlete may need to be more diligent in terms of his or hers nutrition intake in roder to really make sure that some sessions are ketogenic.
  • Moreover, every athlete needs to consider his or hers target event and also take into account predicted finish time and goal intensity level as both these factors also highly influence what energy source that predominantly will be utilized on race day, and the training and nutrition strategy should be directed towards just that.

Final nutrition advice

45:05 -

  • In general I think that one should aim to eat a balanced and varied diet and don’t forget to enjoy the food and/or the company that comes with eating!

    In some certain situations your nutrition can be directed to achieve a specific performance outcome but this should not be the case all the time, I think that some of the healthiest and top performing elite athletes also have this approach in many cases.

Improving nutrition research

47:55 -

  • I think that having relevant outcome measurements such as performance is really important.
  • Another aspect could be a more nuanced discussion in terms of what diet ”is the best”, there are no such thing as ”the best diet”, it all depends on the athlete, goals, event etc. etc.

Rapid fire questions

49:40 -

  • What is your favorite book, blog or resource related to endurance sports? I am a big Alex Hutchinson as well David Epstein fan but I also really like the Science in Sports website, between these three I can always find something interesting.
  • What is a personal habit that has helped you achieve success? Perseverance and applying things on myself and constantly be willing to change my opinions over time.
  • What do you wish you have known or done differently in your career? I used to believe that scientists and researchers knew more than coaches and athletes but know I have realized that they all contribute in an equally important way and I have started to take more input from coaches and athletes lately, which have been really educational and I wished I had done more of earlier.

​LINKS AND RESOURCES:


Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal. Please contact me if you have feedback on the podcast or want to make suggestions for improvement or send in a question for a Q&A episode. If you are a long-time listener and appreciate the value the podcast brings, please consider taking a couple of minutes for leaving a rating and review on iTunes/Apple Podcasts, or wherever else you can think of leaving a rating and review.

Mikael Eriksson

ReCENT EPISODES:

July 13, 2020

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