I recently finished reading What The Fat? Sports Performance: Leaner, Fitter, Faster on Low-Carb Healthy Fat by Schofield, Grant; Zinn, Caryn; Rodger, Craig (2015-12-02) The Real Food Publishing Company. Kindle Edition. Although this book is aimed at the community of athletes, I was drawn to it by Jeff Volek’s introduction:

Grant, Caryn and Chef Craig walk the talk. They do scientific studies on low-carb diets, work with real athletes, and practice what they preach. Simply put, they are credible and wise. Unlike so many other diet books spewing garbage about nutrition, they are not overly dogmatic and openly admit when they don’t have all the answers. They are open-minded, intellectually flexible, and have a balanced perspective on what in reality is an enormously complex topic. As they repeat over and over in the book, science can only take us so far. Each person needs to experiment for themselves and find out what works and what doesn’t. (Kindle Locations 40-44).

I had read Volek & Phinney’s The Art and Science of Low Carbohydrate Performance and wrote a Blog Post on it. That book is now a solid 3 years old and there is a ton of new information and experience on the utilization of a Ketogenic Diet by athletes and their resultant performance.

Most articles on this subject tend to take a black and white point of view – it is all or nothing. Even Volek & Phinney’s work – although hedging their bets – focused on the ill effects of adding carbs to the athlete’s diet. The authors here – focus on metabolic flexibility.

Humans are designed to be metabolically flexible. That is to say, if you want to get the best out of your brain and body then you should be able to rely on fuel from both carbohydrates and fat as and when you need them. Someone who is metabolically flexible can use fat as the primary (and almost exclusive) fuel when they are resting, sleeping and moving around at a fairly slow pace. As they start to move around at a quicker pace – like fast running – they will be able to take advantage of extra fuel supplied by carbohydrate, and when they are going nearly flat out they will rely almost exclusively on carbs for fuel.

We measure metabolic flexibility in our lab using online gas analysis. We measure proportions of inhaled and exhaled oxygen and carbon dioxide to understand just how much fat and how much carbohydrate someone is using from rest to flat out exercise. What you want to see is represented in Figure 1.1; that is, this athlete mostly uses fat for fuel at low running speeds and mostly carbs at faster speeds. This athlete is a male triathlete who has been eating Low-Carb, Healthy-fat for over two years. He is highly metabolically flexible. (Kindle Locations 474-483). 

One of the more fascinating concepts was first brought out by Volek and is emphasized here – and that is the body’s ability to produce its own glucose in the absence of carbs.

Jeff Volek’s recent work in the FASTER {Fat-Adapted-Substrate oxidation in-Trained-Elite-Runners} study … shows that in well-fat-adapted endurance athletes, muscle glycogen (carb) stores can actually be replaced just as efficiently as that of non-fat-adapted athletes even without eating carbs. This happens because glucose re-synthesis genes are up-regulated in fat-adapted athletes.

This result is a big deal and the first work of its kind to show it. Fat-adapted low-carb endurance athletes were as good at getting glucose back into their muscles as high-carb athletes even though they didn’t eat any extra glucose.(Kindle Locations 787-796).

The authors re-emphasize all of the benefits of a Ketogenic Diet. But the most important aspect is the actual stories of how endurance and high class athletes utilize a LCHF diet for training and then when and how they add carbs for parts of a race.

Overall take homes

  • The LCHF nutrition approach is feasible for high-performance endurance racing, including Ironman.
  • The application at this level requires carbohydrate ingestion during the event itself.
  • Carbohydrate loading beforehand wasn’t necessary.
  • Heat chamber training may have been beneficial for performance.
  • Monitoring training load and output during training and racing was useful, especially power on the bike. (Kindle Locations 1120-1126). 

The authors provide real examples and stories of various athletes – not just runners. Each of those athletes explores the when and how they add carbs – if at all – to get their best performance.  The reality is – there is no one simple formula. There is a starting point – to become fully fat adapted.

The authors provide you with the tools necessary for you – as an individual – to determine how to apply the addition of carbs in your sport – so that you can win the race. I believe that any one who trains endurance athletes needs to read this book. The days of “Carb Loading” are numbered.

Bottom line – this is an excellent read – and worth the time and effort to apply the lessons learned to your life.