How to Train Your Body for 90g of Carbs Per Hour
Nutrition

How to Train Your Body for 90g of Carbs Per Hour

Building Digestive and Metabolic Tolerance for Long-Distance Performance

For years, endurance runners were told that 30–60 grams of carbohydrates per hour was the practical limit.

Today, sports nutrition research shows that well-trained athletes can absorb and oxidize up to 90 grams per hour — sometimes more — when combining multiple carbohydrate sources.

But here’s the reality:

Your legs may be ready for 90g per hour.
Your aerobic system may be ready.
Your body as a whole may not.

Late-race fatigue is often blamed on fitness. Sometimes it’s fuel delivery capacity. Learning to handle high carbohydrate intake is a trainable adaptation — just like pace, cadence, or endurance.

Why 90g Per Hour Matters for Runners

Carbohydrate availability is one of the primary determinants of sustained performance in events longer than 90 minutes.

Position stands from the International Society of Sports Nutrition and the American College of Sports Medicine support carbohydrate intake during prolonged exercise to improve performance and delay fatigue.

Research consistently shows:

  • 30–60g/hour improves endurance compared to no fueling
  • 60–90g/hour increases carbohydrate oxidation rates
  • Combining glucose and fructose enhances absorption and utilization

In practical terms:
Higher carbohydrate availability allows runners to sustain intensity deeper into long efforts.

But only if the body can tolerate it.

What “Handling 90g Per Hour” Actually Means

Training your body to handle high carbohydrate intake involves more than just digestion.

It requires adaptation across several systems:

1. Digestive Capacity

The small intestine absorbs carbohydrates through transport proteins (primarily SGLT1 for glucose and GLUT5 for fructose). Repeated exposure increases transporter expression and efficiency.

2. Gastric Emptying

Your stomach must empty fuel into the intestine efficiently. Highly concentrated solutions or unfamiliar intake patterns slow this process.

3. Fluid Balance

Carbohydrate absorption depends on adequate hydration. Poor fluid strategy increases gastrointestinal discomfort.

4. Metabolic Utilization

Once absorbed, carbohydrates must be oxidized efficiently by working muscles. Higher intake improves availability — but your training determines how effectively that fuel is used.

Handling 90g/hour is a full-system adaptation.

Why Runners Struggle With High Carb Intake

Common race-day symptoms include:

  • Stomach fullness
  • Sloshing
  • Side cramps
  • Nausea
  • Inability to continue fueling

These are rarely caused by “bad products” alone. More often, they result from:

  • Jumping from low intake to high intake
  • Inconsistent fueling patterns
  • Inadequate hydration
  • Lack of progressive exposure

The body resists what it hasn’t practiced.

A Progressive Framework to Reach 90g/Hour

The goal is gradual adaptation — not sudden overload.

Phase 1: Establish Consistency (30–45g/Hour)

During long runs over 75–90 minutes:

  • Fuel every 20–30 minutes
  • Maintain consistent intake
  • Practice with intended race products

Focus on rhythm.

Phase 2: Increase to 60g/Hour

After 2–3 weeks of stable fueling:

  • Raise intake gradually
  • Maintain hydration
  • Monitor comfort

Most runners stabilize here with practice.

Phase 3: Introduce Multiple Carbohydrate Sources (75g/Hour)

To move beyond 60g/hour:

  • Combine glucose-based gels with fructose-containing drinks
  • Use products formulated with 2:1 glucose-to-fructose ratios

This utilizes multiple intestinal transport pathways and increases total absorption capacity.

Phase 4: Practice Under Intensity (80–90g/Hour)

Absorption differs at race effort compared to easy pace.

Once tolerance is stable:

  • Practice during long-run progression finishes
  • Test fueling during tempo sessions
  • Replicate race-day pre-run meals

Handling 90g/hour under intensity is the final adaptation layer.

How Long Does Adaptation Take?

Most runners notice meaningful improvement within 2–4 weeks of consistent practice.

Adaptations include:

  • Increased transporter expression
  • Improved gastric emptying efficiency
  • Reduced perception of GI distress

Like aerobic fitness, this capacity declines if not maintained.

Is 90g Per Hour Necessary for Everyone?

Not necessarily.

Higher intake becomes most relevant for:

  • Half marathons at aggressive pace
  • Marathons
  • Ultramarathons
  • Long trail races

For shorter events, 40–60g/hour may be sufficient.

Carbohydrate intake should match event duration and intensity.

The Bigger Performance Picture

Many runners train:

  • Their aerobic engine
  • Their threshold
  • Their cadence
  • Their pacing discipline

Few train their fueling capacity.

When pace collapses late in a race, it is not always a fitness limitation. Sometimes it is a fuel delivery limitation.

Training your body to handle 90g of carbs per hour increases the ceiling of sustainable effort.

Fitness determines potential.
Fuel availability determines how long that potential can be expressed.

And in long-distance running, that difference matters most when fatigue sets in.