Review of High-Carb vs Low-Carb Approaches for Endurance

Few debates in sports nutrition are as heated as carbs vs fats. Should endurance runners rely on a traditional high-carb diet, or adopt a low-carb, high-fat (LCHF) approach for better fat-burning?

High-Carb Benefits

• Fuel for High Intensity: Carbs are the body’s preferred energy source.
  
  
• Proven Science: Most elite runners thrive on high-carb diets.
  
  
• Easier Recovery: Carbs replenish glycogen quickly.
  
  

Low-Carb Benefits

• Fat Adaptation: Trains the body to use fat stores, delaying glycogen depletion.
  
  
• Reduced GI Issues: Some report fewer sugar spikes and crashes.
  
  
• Steady Energy: Helpful in ultra-distance events.
  
  

Challenges of Low-Carb

• Reduced Speed: Glycogen is essential for high-intensity running.
  
  
• Adaptation Period: Early fatigue and “low-carb flu” are common.
  
  
• Limited Evidence for Performance Gains: Research is mixed.
  
  

Verdict

For most runners, high-carb remains king — especially for races under marathon distance. Low-carb may have a niche role in ultra-endurance, but it’s not a universal solution.

- Edward