The Low Carb, High Fat Diet: Is it beneficial for endurance performance? With Professor Louise Burke

The question being asked today is “Is a low carbohydrate, high fat diet the future of endurance sport?” 

And to answer that I asked one of the sports nutrition greats, Professor Louise Burke OAM, to weigh in.

Louise Burke is an Australian Sports Dietitian with 40 years of experience. She worked at the Australian Institute of Sport (AIS) for thirty years, first as Head of Sports Nutrition and then as Chief of Nutrition Strategy and I was very fortunate to work under her during my fellowship at the AIS.

She has contributed over 350 papers in peer reviewed journals & book chapters and was awarded a Medal of the Order of Australia in 2009 for her contribution to sports nutrition. 

She is the Chair of Sports Nutrition in the Mary MacKillop Institute of Health Research at Australian Catholic University in Melbourne and leads their Supernova Project - high level research that produces quality answers to some of the critical questions in sports nutrition. Working with and studying endurance sports athletes, they study the different approaches to supporting intensified training including the low fat, high carb diet (keto), a high carbohydrate diet and a periodised carbohydrate diet, to see which best promotes athletic performance in high performance endurance sport.

I challenge you to find anyone more qualified to comment on the LCHF diet and whether or not it’s beneficial for endurance performance. Here’s a summary of our conversation:

Why are we so obsessed with the LCHF diet & endurance performance?

• People (and triathletes) like change and want to be seen as new thinkers or “special”.
• They are easily marketed as they like to adopt new things.
• Need to be wary of fake news, social media amplification of simple idea, celebrity endorsements.
• Some prefer to ignore the evidence, stubbornly keep their head in the sand and use confirmation bias to uphold their opinion.
• Follow the research instead. 

I was fortunate to assist with some of the data collection and food provision during ‘Project Supernova’ 1 – the first study you ran with the elite race walkers. Since then, there have been six more Supernovas, with a seventh planned. What questions did this research set out to answer?

Our first Supernova studies where about "This is what a diet that has persistent high carbohydrate availability might offer. This is what having a periodised approach to carbohydrate might offer. And here's the keto diet". And we gave all the pros of those different approaches. And we said to athletes, "What do you think might work for you?

They selected their preferred diet, then, done over two camps and four races (to manage numbers):

• We controlled every morsel of food they consumed over the period of the studies.
• A three week implementation of these diets with testing pre and post. So by the time they did their races, those that were in the keto group had been on the keto diet for three and a half weeks.
• Tried to replicate the only other study - the Finney study from the 1980s, which had been done with cyclists.
• Put it into real life context in really rigorously controlled circumstances with the athletes actually doing real races.
• Athletes competed in a 10,000 metre track race, pre and post interventions – a real race with prize money, able to post PBs, race judges, all the things that go with real life races.
• Did other testing to see what was happening with metabolism to try and explain our findings of the race outcomes.

What were the results? What did you find?

• Overall, each of the groups of athletes had improved their VO2 Max over the approx. four weeks of the camp.
• Each got the same sort of benefit of about a 5 - 6% improvement in their VO2 Max - that was the beginning of the season – doing intensified training and getting benefits.
• BUT only the groups that trained and raced with the high carbohydrate or the periodised carbohydrate approach improved their race performance.
• The ketogenic diet group remained about the same.
• The high carb group, the high carb diet was a better support mechanism for both training and the racing. 

At Supernova 2 the following year however, the study was run with all the athletes in the one camp/two races – so they had the same environment and same experience.

• We saw exactly the same results with getting that improvement in VO2 Max over the training.
• But this time, the ketogenic diet group had an impaired race performance compared to race one, and
• The high carbon periodised groups improved their performance
• The differential between race one and race two with both Supernova 1 and Supernova 2 was about 8%.
• There was an advantage of about 8% to have done the races and training with carbohydrate support.

Subsequent Supernova studies, where things like adding carbohydrates on race days, race days with Ketone Ester supplements were tested, etc still resulted in an 8% differential between the carb group and the Keto group.

FINDINGS: There's a problem with doing higher intensity endurance performance with the ketogenic diet.

If you're at the higher intensities of exercise, where you're working at very high amounts of your VO2 Max, whatever oxygen you can get the muscle, if you're burning carbohydrate, you'll get more ATP, and therefore more speed, than if you're burning fat - it's just about the fuel ability to work with oxygen and produce power.

If you're doing sports where higher intensity exercise at a higher percentage of VO2 Max is required, then you want the most efficient and economical fuel source, that every bit of oxygen that you can deliver to the muscle, to get maximum bang for its buck in terms of fuel conversion to ATP.

What questions are still left unanswered?

Consider how events are won, what tactics are required to get to the line first, what intensity is needed when and how to support that higher intensity with carbohydrate fuels to increase that VO2 Max.

Do we see any difference to performance in the literature from going from keto to then fuelling with carbohydrate on race day?

We still found an impairment of performance in the higher intensity domains. And that's because when you are keto adapted, you downregulate your ability to use carbs.

When you've downregulated just can't put the same amount of carbohydrate oxidation through the system.

There's no way of being optimally carb adapted and fat adapted at the same time, you've got to choose which one becomes the more important.

If you're keto adapted, you need several days to get to the adaptation, but you can't undo that with one session properly to be able to fully use carbohydrates. Approx. five or six days to fully return back to being able to burn carbohydrate in well trained athletes, longer with lesser trained.

It's a matter of understanding what your event is, what your particular circumstances are and seeing the best mix.

Some keto people often do still include carbs in around their training sessions to be able to train at higher intensities and on race day as an extra fuel source.

One of the things we should be promoting in sports nutrition is that it's not a one size fits all approach. There are all different sorts of nuances and context to the way that athletes should think about their race plans.

Work with a good Sports Dietitian who understands all those nuances to find the best fit for you.

Can you give me a one word answer – does LCHF enhance endurance performance?

No. Qualifier - in most situations, no, it won’t.

To dive deeper into Professor Burke’s findings, listen to the Triathlon Nutrition Academy Podcast, EP 79 - The Low Carb, High Fat Diet: Is it beneficial for endurance performance? With Professor Louise Burke  

Links to some of Professor Burke's key papers can also be found in the podcast show notes.

If you are interested in learning more about the Triathlon Nutrition Academy Program and what it can do for you, head HERE to join the waitlist for our next opening.