Will avoiding carbs make me a better athlete?

Jul 27, 2017 | Performance | 0 comments

In recent times, Low Carb and Ketogenic diets have become hugely popular. These are diets where (as the name suggests) you don’t really eat carbs and you eat lots of protein and fats. Why? Essentially, to shift the body to a state where fat is the preferred fuel source. This article will focus on whether or not this is beneficial for athletic performance.

Hold up

Whilst burning fat as a fuel source may seem great, we must remember that most of the time, we already are burning fat as a fuel source. This is what the body prefers to burn as a fuel at low intensities.

It seems that the purpose of a Ketogenic diet is to increase the body’s capability to utilise fat as a fuel source, and it’s been hypothesised/reported that during intense and prolonged exercise you can perform better. What does the research say?

Fat Burning and Intense Exercise

When we exercise at very high intensities, the body prefers to burn carbohydrates. This is due to the fact that it can be broken down into glucose more readily, helping us to perform maximal efforts for a prolonged period. In substrate utilisation tests (tests which determine whether you’re using fat or carbohydrate and at what intensity), we see that at very high heart rates, the body is looking to burn carbohydrates. However, the research does seem to show that at heart rates as high as 80%, fat can be readily used as a fuel source, provided you’re adapted to a high-fat diet.

What adaptations are we after?

As athletes, we’re looking to enhance our performance for certain skills and movements, at high intensities. It’s usually at very high intensities, that the body is exposed to the stressors needed to cause us to adapt.

So at 80% of Max Heart rate, and often above.

It’s usually at these intensities that carbohydrates are burned as a fuel, to supply the glucose needed. If we don’t obtain the glucose needed to perform at these high intensities, we may not be able to access the intensity needed to ensure that we are adapting in a manner to enhance our performance goals.


Glucose isn’t just obtained from carbohydrates. Glucose can be obtained from protein, in a process called Gluconeogenesis. So, can we do away with carbs and obtain all of our glucose from protein? If so, would gluconeogenesis be increased for those on a high-fat diet?

In a recent study, endurance cyclists were studied, as it was hypothesised that cyclists who were on a low carbohydrate and high-fat diets would show higher rates of gluconeogenesis. The study found that this was not the case, with the researchers stating that,

“The finding that GNG (gluconeogenesis) was similar between groups during exercise was somewhat surprising because it has often been speculated that LCHF athletes would rely primarily on newly synthesized glucose from fat- and protein-derived precursors”

So how does this translate to performance?

Let’s return to performance. In this study, it was demonstrated that when it came to short-term fat adaptation, those on a high-fat diet, had increased ratings of perceived exertion. In essence, their sessions felt more challenging. As athletes, we want to offset feelings of difficulty and fatigue as much as possible, in order to give us the edge.

In this study, it was found that performance was impaired in elite endurance athletes who had adapted to a high fat (ketogenic) diet.

So, if we’re after improved athletic performance and adaptations associated with improved athletic performance, it may be wise to include carbohydrates in our diet.

Whilst performing at an elite level is clearly possible on a high-fat diet, getting into and maintaining ketosis is difficult- both psychologically and physically, unnecessary and not necessarily advantageous.

We’d recommend that you choose a diet that enables you to perform to your optimum. At present, we think a balanced diet, high in protein with a good amount of both fats and carbohydrates will do the trick.


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