Half Ironman Nutrition Plan: Complete 70.3 Fueling Guide

Half Ironman nutrition requires consuming 60-90 grams of carbohydrates per hour during the bike leg and maintaining hydration to fuel 4-7 hours of continuous racing.

At 70.3 distance, nutrition becomes the "fourth discipline." Get it right and you'll race strong to the finish. Get it wrong and you'll be walking by mile 10 of the run.

Why Nutrition Matters in 70.3

The Energy Math

Without proper fueling, you WILL bonk.

The Difference from Shorter Races

Pre-Race Nutrition

Week Before

Carb Loading (Final 2-3 Days)

For a 70kg athlete: 490-700g carbs per day

Day Before Race

DO eat:

• White rice/pasta
• White bread
• Pancakes
• Bananas
• Pretzels
• Sports drinks

DON'T eat:

• High fiber foods
• Spicy foods
• New/unusual foods
• Heavy fatty meals
• Large amounts of protein

Race Morning

Timing: 3-4 hours before start

Amount: 2-3g carbs per kg body weight (140-210g for 70kg athlete)

Sample Breakfast:

- Oatmeal (80g carbs)
- Banana (30g carbs)
- White toast with honey (40g carbs)
- Sports drink (30g carbs)
Total: ~180g carbs

Post-breakfast, pre-race:

• Sip water/sports drink
• Small gel 15-30 min before swim (optional)
• Nothing heavy

Race Day Nutrition: The Swim

During the Swim

Eat: Nothing Drink: Nothing

You can't eat during the swim. Focus on:

• Relaxed breathing
• Efficient stroke
• Setting up for T1

T1

Quick transition—no time to eat. Maybe:

• Quick sip of water
• Nothing that requires chewing

Race Day Nutrition: The Bike (Critical!)

Fueling Targets

Timeline

What to Consume

Sports Drink (easiest):

• 30-40g carbs per bottle
• Drink throughout
• Provides fluid + carbs + electrolytes

Gels:

• 20-25g carbs each
• Every 30-45 min
• Take with water
• Practice in training!

Bars/Chews (early in ride):

• 25-40g carbs
• More satisfying
• First 60-90 min only
• Harder to digest later

Sample Bike Nutrition Plan (3-hour ride)

Total: ~180-200g carbs (60-70g/hour)

Hydration Strategy

Calculate sweat rate in training:

1. Weigh before ride (kg)
2. Ride 1 hour (note fluid intake)
3. Weigh after ride (kg)
4. Weight loss (kg) + fluid intake (L) = sweat rate (L/hour)

Typical targets:

• Cool conditions: 500ml/hour
• Moderate: 600-700ml/hour
• Hot: 750-1,000ml/hour

Race Day Nutrition: The Run

Fueling Targets

Aid Station Strategy

Gel Strategy on Run

What Works Best on the Run

After 3+ hours of racing, your gut is stressed. Best options:

• Sports drink (easiest to digest)
• Gels (if practiced)
• Cola (caffeine + sugar, easy on stomach)
• Flat cola (less carbonation)

Avoid: Solid foods, untested products

Common Nutrition Mistakes

1. Not Eating Enough on Bike

The mistake: Only 30-40g carbs/hour The result: Bonking on run The fix: Target 60-90g/hour from start

2. Starting Fueling Too Late

The mistake: Waiting until hungry The result: Already behind on energy The fix: First fuel at 15 min, schedule from there

3. New Products on Race Day

The mistake: Using race-provided nutrition you haven't tested The result: GI distress, vomiting The fix: Practice with YOUR products

4. Ignoring Hydration

The mistake: Only drinking when thirsty The result: Dehydration, cramping The fix: Scheduled drinking every 10-15 min

5. Overdrinking

The mistake: Drinking too much plain water The result: Hyponatremia (low sodium) The fix: Include electrolytes, especially in heat

Practice in Training

Every Long Session

Practice your race nutrition:

• Same products
• Same timing
• Same amounts
• Note any issues

Brick Workouts

Critical for testing run nutrition:

• What works after bike fueling?
• Can you handle gels?
• Aid station practice

Adjust and Refine

• Start conservative
• Increase if tolerating well
• Decrease if GI issues
• Find YOUR formula

Special Considerations

Hot Weather

• Increase fluid to 750-1,000ml/hour
• More sodium (add electrolyte tablets)
• Consider ice in bottles
• Dump water on yourself

Cold Weather

• Still need carbs
• May drink less
• Warm fluids if possible
• Don't skip nutrition

GI Issues

If you're prone to stomach problems:

• Avoid high fiber day before
• Stick to easily digestible foods
• More liquid calories (sports drink)
• Smaller, more frequent intake

Race Week Checklist

3-4 Days Before

• Begin carb loading
• Buy race day foods
• Prepare bottles
• Pack nutrition bag

Day Before

• Low fiber meals
• Prep race morning breakfast
• Fill bike bottles
• Organize gels/bars

Race Morning

• Eat 3-4 hours before
• Small snack 1-2 hours before
• Stay hydrated (not over-hydrated)

Related Resources

• 70.3 Calculator - Race time prediction
• Half Ironman First Timer Guide - Complete beginner guide
• 16-Week Half Ironman Plan - Training program
• Triathlon Bike Nutrition - Bike fueling details
• Triathlon Run Nutrition - Run fueling details