Carb Intake Science Simplified

Carbohydrates: The Endurance Athlete's Primary Fuel

For decades, carb intake recommendations have swung between extremes. Let's cut through the noise and look at what the science actually says.

The Basics

Carbohydrates are stored as glycogen in muscles and the liver. During exercise:

• Low intensity (<60% VO2max): Fat is the primary fuel
• Moderate intensity (60-80%): A mix of fat and carbs
• High intensity (>80%): Carbs dominate

How Much Do You Need?

Research consistently shows these guidelines:

The Dual-Transport Advantage

Your intestine can only absorb ~60g of glucose per hour through SGLT1 transporters. By adding fructose (absorbed via GLUT5), you can push total absorption to 90-120g per hour.

This is why modern sports nutrition uses 2:1 or 1:0.8 glucose-to-fructose ratios.

Practical Application

Calculate your hourly carb target based on duration and intensity

Choose products with glucose-fructose blends

Start with lower amounts and train your gut to tolerate more

Always combine with adequate hydration

The Bottom Line

More is often better — but only if your gut can handle it. Train your nutrition strategy as rigorously as your physical training.