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Has going Low Carbohydrate affected my performance?

Posted by Charles Lubbe on

Has going low carbohydrate affected my performance. I feel that I need to answer the question focusing on four aspects

  1. Have I corrected my weight, health and serum lipids?
  2. Has my performance on low carb increased?
  3. Has my weight, health and serum lipids been easier to sustain than high carb
  4. Could I have performed better had I kept on high carb or could I improve my current performance by going higher carb?


While I have participated in various forms of adventure and athletics all my life I previously never paid attention to why I was gaining weight or the effect it was having on my health.  I have also never been particularly good at any forms of sport but rather participated for the enjoyment of it. The year is 2014 and my weight sky rocketed to 115kg and 39% body fat. I was pre-diabetic. The recommended diets were not helping.

In my first year of correcting my weight, health and serum lipids on low carb I entered IM PE 2015. I set myself two goals. One was to complete and the second was to participate on fat only. At the start of IM 2015 I had lost 30kg and my health markers were much improved. I completed the race in 16h 49 minutes. The longest day of my life. This was 2 hours slower than my previous IM. Could it be that I was so slow racing on fat or was it poor preparation?

In 2016 I participated in IM 2016 and the Sky Run. I completed IM in 13h 50 or 3 hours faster than 2015. It was also a similar time to my high carb IM six years earlier. My weight, health and serum lipids were stable with my fat percentage significantly dropping. I completed Skyrun in 29 hours 49 minute. An even longer day. The fuel of choice was fat.  I had completed many shorter distances on fat during 2016 and was happy that I could keep moving below threshold for an extended period.

IM 2017 and my time improved to 13h05. Three hours and 49 minutes faster than my 2016 time and my fastest marathon and IM to date. All on high fat low carbohydrates. In my final preparation for Comrades and as pretty much a non-runner,  I ran my first qualifying time of 4h17 minutes and I’m looking forward to breaking 4 hours before November.  Comrades shortly after IM was an easy laid back rather slow affair at 11h 49 minutes. I have every expectation that I will complete a full IM under 12 hours a Comrades under 9. No records are going to be broken however :)

This year I will take on Skyrun again as well as all the races I did last year to monitor a direct increase in performance but it’s clear to me that my performance is improving while my weight, health and serum lipids are improving and the gains easily sustained. Recovery on low carb is phenomenal as the oxidation is a lot lower. I am running 200 and 400 m sprints at similar speed to when I was 16.

There is also much said about not being able to maintain strength and conditioning activity on high fat. As a Cross Fit coach and box owner I am continually seeing injury free gains.

I have recently asked myself the question whether using carbohydrates would have seen me getting better results? To answer this question, I have looked at the performance improvement over time of many of my peers and mid-range athletes and cannot see any direct correlation between what they are fueling with and their performance. The reason I say this is that I assume if carbohydrate played a significant role over time that I would be left lagging further and further behind. I would also not see huge improvement in my own times which is clearly not the case.

I must conclude that fuel itself does nothing for substrate and that the only time I wold need to rely on carbohydrates would be racing above threshold and or when I am taking on an activity that I am ill prepared for.  I cannot see how I could give up the corrected health, weight and serum lipids improvements in favor of potentially and increase in performance.

Low carbohydrate has not only allowed me to participate far beyond all expectation but also improved the quality of my life.

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