Low Carb High Fat

Low carb, high fat, fat oxidisation, periodisation….
​All different ways of eating and approaching training and all claiming they are THE BEST! Are you just a bit confused?

Well the really good news is that we have some new science investigating the effects of these diets on world class race walkers and their performance benefits.

We took the chance to discuss the latest results with Catalyst Dietitians David Bryant and Alex Dreyer… read on for their great interpretation and balanced application of these results.

What type of diets did they compare in this 3 week study? 
The walkers ate either a high carb diet (60-65%), high fat diet (75-80%) or periodised high carbs (60-65% carbs but spread differently according to training needs).

What was the benefit found in athletes on a high fat diet?
​The athletes on a high fat diet achieved substantial increases in fat oxidation during intense exercise.  This means they were able to burn fat more effectively during these sessions once they were adapted to the high fat low carb diet.
But how did this high fat diet affect performance?
​Adaptation over time to the ketogenic, low carb high fat diet actually impaired exercise economy and so did not transfer into any performance benefit in elite athletes.
Why didn’t being able to burn fat result in a performance benefit?

We know that for easy or steady intensity exercise we use a mixture of fat and carbs as fuel. However at higher intensity the body requires significantly higher contribution of carbohydrates as the energy source.

So therefore if the preferred carbs are not available (as in the high fat low carb athletes in this study), the body will use protein and fat and as a result the exercise intensity will reduce.  The final result as seen in the study was that the low carb high fat diet negated performance benefits.
Does this study change your recommendations for endurance athletes? 

For athletes aiming to train at low intensities there may be some benefit from the ability to oxidise fat, because at low intensity it can be an efficient fuel.

However for athletes training at higher intensity (as required for a triathlon for example), this study suggests that fat adaptation does not carry any performance benefit, and using carb periodisation is still a very effective approach.
You’ve recommended your athletes to become “smart CARBers” – can you explain what this means? 

This means to use carbs strategically pre and post training sessions.  The aim is to maximise carb availability before higher intensity training session and replenish carbs post session to retain muscle glycogen stores.

Then on lower volume, lower intensity days, carb intake can be reduced to maximise fat oxidation during training and to improve body composition (ie burn fat stores on easier days to help maintain a healthy race weight).

At last we have some science around this really interesting area of nutrition!
Enjoy your wholesome, balanced and well fuelled week…

Belinda x