Marathon Fueling Strategy: Hydration and Energy Intake During the Race

Many runners pour countless hours into training, only to fall short on race day because of fueling mistakes. The right fueling strategy can delay fatigue, help you hold your pace, and may even let you speed up in the second half.

1. Why Fueling Matters So Much

The Effects of Dehydration

Dehydration Level	Body Weight Loss	Effects
Mild	1-2%	Elevated heart rate, mild fatigue
Moderate	2-4%	Performance drops 3-8%, impaired judgment
Severe	Over 4%	Risk of heat exhaustion, may require withdrawal

The Risk of Energy Depletion

The human body stores roughly 1,800-2,000 kcal of glycogen. At marathon pace, you burn approximately 65-80 kcal per kilometer (for a 70kg runner). A full marathon burns roughly 2,800-3,500 kcal in total — more than your glycogen reserves — so you must refuel along the way.

2. Hydration Strategy

Pre-Race Hydration

Timing	Recommended Amount
2 hours before the start	500ml of water or sports drink
30 minutes before the start	200ml of water

Do not over-hydrate before the race — it can lead to (dilutional) hyponatremia.

Hydration Rhythm During the Race

Golden rule: Don’t wait until you’re thirsty to drink — by the time you feel thirsty, you’re already mildly dehydrated.

Aim to take in 150-200ml of fluid every 15-20 minutes. Practical tips:

1. Stop briefly at every aid station to drink (drinking while running increases the risk of choking)
2. Drink water before sports drinks
3. Increase your fluid intake in hot weather

Aid Station Spacing in Taiwan Marathons

Major Taiwan races typically place aid stations every 2.5 to 5 kilometers. Some stations offer:

• Water
• Sports drinks (usually Supau or Pocari Sweat)
• Bananas
• Energy supplements (at some races)

3. Energy Fueling Strategy

When to Start Taking In Energy

Recommendation: Start fueling after 45-60 minutes of running — don’t wait until you feel hungry.

Comparing Energy Fueling Options

Fuel Source	Calories	Absorption Speed	Pros	Cons
Energy gel	100 kcal	Fast (15 min)	Easy to carry, easy to digest	Overly sweet, needs water
Energy bar	200 kcal	Moderate	Provides fullness	Time-consuming to chew, harder to digest
Banana	90 kcal	Moderate	Natural, contains potassium	Inconvenient to carry
Dates	70 kcal	Fast	Natural sugar	Sticky, less common
Sports drink	50 kcal/250ml	Fast	Replenishes fluid and electrolytes at once	Insufficient sugar content to use alone

Energy Gel Timing Schedule (Example: 4-Hour Finish)

Time	Distance	Action
15 minutes before the start	0km	1 gel (optional)
60 minutes	~10km	1 gel + water
105 minutes	~18km	1 gel + water
150 minutes	~25km	1 gel + water
195 minutes	~33km	1 gel + water

4. Electrolyte Management

Sweating during a long run causes you to lose not just water but also significant amounts of sodium, potassium, and magnesium.

Symptoms of Electrolyte Deficiency

• Muscle cramps (especially in the calves)
• Dizziness, nausea
• Weakness in the limbs

Recommendations

1. Salt tablets: Take one every 60-90 minutes (containing 300-500mg of sodium)
2. Sports drinks: Choose sports drinks that contain sodium rather than plain water
3. Natural salt: Japanese runners often carry small salt packets, which work just as well

5. Pre-Race Nutrition Plan

The Day Before the Race

• Focus on carbohydrates: rice, noodles, bread
• Avoid high-fiber, high-fat foods
• Reduce vegetable intake (to lower digestive load)

Race-Day Breakfast (2-3 hours before the start)

Recommended combinations:

• A bowl of rice + scrambled eggs
• Or: oatmeal + banana
• Or: 2 slices of white toast + peanut butter + sports drink

Avoid: fried foods, high-fiber vegetables, dairy products (which may cause gastrointestinal discomfort)

6. Handling GI Distress During the Race

Approximately 30-50% of marathon runners experience gastrointestinal issues (side stitches, nausea, diarrhea):

1. Slow down: Temporarily reduce intensity to let your stomach recover
2. Pause fueling: Skip 1-2 aid stations
3. Diaphragmatic breathing: Helps ease side stitches
4. Practice in advance: Train with the exact fuel you plan to use on race day

7. Building a Personalized Fueling Plan

It’s recommended that 6-8 weeks before the race, you fully simulate your race-day fueling plan during long training runs to find what works best for you. Everyone reacts differently to different brands and flavors of energy gel, so you must test them before race day.

Conclusion

There’s no one-size-fits-all formula for marathon fueling, but “fuel early, and often, in small amounts” is the common principle behind every strategy. Start practicing your fueling plan on your next long run — on race day, you’ll thank yourself for the preparation.

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