How to Become a Fat Adapted Athlete (and Smash Your PBs)

Fat Adaptation 101

Fat adaptation is the metabolic reorchestration from a predominant fuel source of glucose to a predominant fuel source of fat.

This is the normal, preferred metabolic state of the human. Before the food pyramid created the obesity epidemic, humans were in an constant yearly cycle of fat adaptation, based on factors such location, climate, season and food supply.

Some food for thought:

  • Fat adaptation means you can effectively burn stored fat for energy throughout the day. Even the leanest person who weighs 60kg with 10% body fat, has 6kg of fat or 6000g, which at 9 calories/gram is 54,000 calories to potentially access.
  • For athletes, fat adaptation also means you can rely more on fat for energy during exercise. This offers a glycogen sparing effect, so this carbohydrate stored in the muscle is available to support high intensity (where it is most required).
  • For endurance athletes, this is most significant. A simple equation to consider is (and we’re using round numbers here):

Even if you are a very well trained athlete with 2000 calories of muscle glycogen stored, if you are a sugar burning, who burns 1000 calories/hour, you’ll obviously run out of fuel at beyond 2 hours. Even if you’re consuming able to consume 300 calories/hour, there’s still a 700 calorie deficient. You don’t need to replace everything you burn, but the inability to tap into our fat reserves is what causes a ‘nutritional bonk’ or ‘hitting the wall’. If you are an endurance athlete whose splits just get slower and slower in a marathon off the bike or ultra marathon, you need to work on your fat adaptation so you essentially never run of fuel.

Becoming a Fat Adapted Athlete

The two basic strategies are as follows:

  • A lower carbohydrate, higher fat (LCHF) approach is particularly useful to enhance fat adaptation, as it decreases your physiology of being a “sugar burner” (that comes with a high carbohydrate intake) and allows for five or more hours between meals based on the satiety and blood sugar response it creates. This allows for metabolic efficiency on a day-to-day basis and ensure your can access fat for the majority of the time and rely on carbohydrates in periods of high intensity. A very general guide is a total intake of 15% carbohydrates, 20% protein, and 65% good fats per day.
  • The second is fasted training, or training empty. When practiced in training (ideally in the ‘off-season’) for 8-12 weeks, this enhances your fat utilisation and decreases your reliance on exogenous fuel sources (i.e. gels). To begin with, start with lower intensity sessions of 60-90 minutes in duration. As your fat adaptation progresses, gradually extend this out to two or two and half hours. Beyond this is often unnecessary as we need to avoid catabolism (muscle breakdown) that can occur over extended durations.

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