One of the biggest fears for endurance athletes is "hitting the wall" — that sudden energy collapse when glycogen stores run out. But smart athletes don't just stuff themselves with more carbs. They train their bodies to spare glycogen by burning fat more efficiently.
This is known as glycogen sparing, and it's a critical tool for anyone racing beyond the two-hour mark.
What is Glycogen Sparing?
Glycogen sparing refers to the body's ability to conserve glycogen by relying more heavily on fat oxidation during exercise.
When you spare glycogen:
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You have more reserve available for high-intensity efforts.
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You delay exhaustion dramatically.
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You maintain more consistent output over time.
How Fat Adaptation Enhances Glycogen Sparing
Low-carb and ketogenic diets train the body to maximize fat usage during submaximal exercise (60–70% VO₂ max).
Result:
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Glycogen is saved for when it’s truly needed (sprints, hills, late-race surges).
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You avoid "sugar dependency" that can cripple performance in long events.
Example from FASTER Study:
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Even after 3 hours at moderate intensity, fat-adapted athletes preserved muscle glycogen levels while still maintaining performance output.
Related reading: Why More Athletes Are Turning to Fat as a Primary Fuel Source
Why Glycogen Sparing Matters in Endurance Sports
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A typical human stores ~2,000 kcal worth of glycogen — but 40,000+ kcal of fat.
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Tapping fat reserves early and often means prolonged endurance without frequent refueling.
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Avoiding glycogen depletion reduces mental fatigue, muscle cramping, and energy crashes late in races.
How to Train for Better Glycogen Sparing
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Low-Carb or Cyclical Ketogenic Diets: force the body to optimize fat use.
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Aerobic Base Training (Zone 2): teaches muscles to burn fat efficiently.
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Long, Slow Training in Fasted State: reinforces fat oxidation pathways.
Transitioning takes time — typically 4–6 weeks — but the long-term payoff is massive for ultra-endurance performance.
Related reading: Training Your Fat Engine: How to Build Aerobic Base for Maximum Fat Oxidation
How Holyfat Supports Glycogen Sparing
Holyfat fuels are specifically designed to supply stable, long-burning fats — keeping your energy high while minimizing the need for constant carb hits.
Train smarter. Spare your glycogen. Go the distance.