Fat adaption is interpreted as Low Fat or Keto by many endurance athletes. Although a Fat Adapted athlete may require fewer carbohydrates in some training sessions, it is less about reducing carbohydrates and more about adapting the metabolic system to use the best fuel source for the intensity of the performance.

For performance over a longer duration, around 4+ hours, fat is optimal as the primary fuel source. Under 2.5 hours and carbohydrate is preferred. It should be noted that we always using both, it is the ratio that changes.

For years we have been advised that carbohydrate / Glycogen is always the best primary fuel source. This has been debunked in many scientific studies with evidence showing the sustained aerobic intensity is best fuelled through Fat Oxidation. In recent times most have been consuming carbohydrates in every training session and all meals in between with the goal of high performance and recovery every session. This has effectively reduced the ability to oxidize fat as a fuel at any intensity. This trend has contributed significantly to the obesity crisis. Fat Adaption is about resetting our metabolic systems to utilize the appropriate primary fuel system for the intensity and stress level of the performance.

Some key points when considering Fat Adaptation:

  • Fat Adaption relates to the whole diet, changing the exercise fuel only will not work if we consume high GI carbohydrates all day.
  • You will not use Fat Oxidation as a primary fuel if you are always in a high-stress state. High stress will ensure you burn Glycogen / Carbohydrate due to the fight or flight stimulus.
  • During Base training, we do our longer session with limited carbs. None up to 1.5 hours, optional up to 2.5 hours, max 60gm per hour over 2.5 hours. This optimizes our bodies ability to oxidize fat and essential criteria for events over 4 hours.
  • During the build phase (around 8-12 weeks out from key events) we practice onboarding the fuel needed for race day, generally 60 grams carbohydrates per hour.
  • We always take some quality carbs before high-intensity sessions where we push into zone 5, above our anaerobic threshold. They help us push the limits using the fight or flight stimulus to maximize force and strength adaptations.

Fat adaption is not about carbs being bad, vegetarianism, veganism, paleo, carnivore or any other diet. All can be adopted and still get Fat Adapted. My preference is to just eat real food, minimizing processed foods.

Getting fat adapted is a choice, you can perform with or without it, however, I believe the longer the distance for more the benefits. Let’s not discount the health benefits of removing the dependency on sugar!

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