Carbs, Gels & Electrolytes: Hour-by-Hour Nutrition for Endurance Runners

When you’re pounding the pavement or tackling the trails for hours on end, nutrition isn’t just important—it’s essential. Proper fueling can mean the difference between a triumphant finish line or hitting the dreaded wall. But what does proper nutrition look like for endurance runners? 

This comprehensive guide breaks down hour-by-hour nutrition strategies for endurance runs of varying lengths. Whether you're training for a marathon or preparing for your first ultra-distance race, we’ll explore how to fuel effectively with carbohydrates, electrolytes, and hydration.

Why Nutrition Matters for Endurance Runners

Running long distances requires more than mental grit and well-trained muscles. Endurance efforts deplete your body’s energy stores, water levels, and electrolytes. Without proper fueling, you risk running out of energy ("bonking") or facing dehydration and cramping. That’s why a strategic nutrition plan is critical to keeping you performing at your best, mile after mile.

We’ll explore how to tailor your fueling based on run duration and introduce evidence-backed guidelines for carbohydrate intake, sodium replacement, and hydration.

Nutritional Needs for Runs Less Than 90 Minutes

For runs lasting 90 minutes or less, your fueling strategy can be relatively straightforward. Your body has enough stored glycogen (your primary energy source) to get you through shorter sessions without needing mid-run fuel.

Carbohydrate Needs

• Requirements: For runs under 90 minutes, there’s typically no need to take in extra carbohydrates during the run.
• Pre-run: Focus instead on a light snack 30–60 minutes before running, such as a banana, toast with peanut butter, or an energy bar (containing 30–50g of carbs).
• Tip: Avoid starting your run on an empty tank, especially if it’s early in the morning.

Hydration

• Drink 8–16 ounces of water 1–2 hours before your run to ensure you’re adequately hydrated.
• Electrolytes generally aren’t necessary unless you’re training in hot, humid conditions. If that’s the case, consider adding electrolyte tabs to your pre-run water or drinking a light sports drink.

Examples of Pre-run Snacks

• 1 medium banana (27g carbs)
• ½ cup of oatmeal with berries (30g carbs)
• A slice of whole-grain toast with honey (30g carbs)

For shorter runs, simplicity is key. Focus on hydration and a pre-run snack, and leave the gels for longer efforts.

Nutritional Needs for Runs Lasting 2-3 Hours

When your mileage extends beyond 90 minutes, your glycogen stores start to deplete. At this point, fueling mid-run becomes essential to avoid bonking.

Carbohydrate Needs

• Requirements: Aim for 30–60g of carbs per hour. This range helps maintain energy levels without overwhelming your digestive system.
• Fuel Types: Gels, energy chews, sports drinks, or even real food like bananas or dates are great options.
• Frequency: Fuel every 30–45 minutes to ensure a steady stream of energy.

Sodium & Electrolyte Replacement

Sweat doesn’t just cause water loss—it depletes key electrolytes like sodium, magnesium, and potassium. Sodium is particularly important for runs lasting over 2 hours:

• Target: 300–500mg of sodium per hour, depending on sweat rate.
• Sources: Electrolyte drinks, salt tablets, or sports gels with added sodium.

Hydration

• Sip water consistently throughout your run, aiming for 16–24 ounces per hour. Adjust depending on temperature and how much you’re sweating.

Examples of Mid-run Fuel

• 1 energy gel (20–25g carbs, ~200mg sodium)
• 1 handful of energy chews (~30g carbs, ~150mg sodium)
• 1 small banana (27g carbs, ~1mg sodium)

Establishing your mid-run fueling routine will help you maintain your pace and energy as you tackle longer sessions.

Nutritional Needs for Runs Lasting 4+ Hours

Ultramarathon or back-to-back long run training? Runs lasting 4+ hours require a robust, well-planned fueling strategy to keep you going strong.

Carbohydrate Needs

• Requirements: 50–90g of carbs per hour. Ultra-distance running often demands higher carbohydrate intake for sustained energy.
• Fuel Types: Mix things up with gels, chews, real foods (like peanut butter sandwiches), and carb-rich sports drinks to avoid flavor fatigue.
• Strategy: Split your carb intake across smaller, more frequent intervals to reduce digestive stress.

Sodium & Electrolyte Replacement

Long-duration runs put runners at risk of hyponatremia (low sodium levels). This is why consistent sodium replacement is critical:

• Target: 500–700mg of sodium per hour. Training in hot or humid conditions? Dial this up.
• Sources: Salt tablets/capsules, sports drinks with added electrolytes, or salty snacks (pretzels or crackers).

Hydration

Longevity on the trails requires maintaining fluid balance:

• Drink according to thirst while aiming for 16–32 ounces per hour.
• Alternate between water and electrolyte drinks to stay hydrated while replenishing electrolytes.

Examples of Ultra Running Fuel

• PB&J sandwich (45g carbs, ~170mg sodium)
• Sports drink (30g carbs, ~300mg sodium per 16 oz)
• Energy gel (20–25g carbs, ~200mg sodium)

For runs of this duration, pack a variety of fuels to keep energy levels high and your stomach happy.

Carbohydrate Intake for Endurance Runs

Proper carbohydrate intake is essential for maintaining energy during long runs. Learn how to fuel your body effectively to enhance performance and avoid fatigue.

Why 30–90g/Hour?

During exercise, carbohydrates are your body’s primary and most efficient energy source. But glycogen stores are limited, meaning you need to replenish them through mid-run fueling.

• 30g/hour suits shorter endurance efforts.
• 90g/hour fits ultra-endurance, where carb oxidation becomes critical.

Popular Carb Sources

• Energy gel = 20–25g carbs
• Serving of energy chews = ~30g carbs
• 1 sports drink (16 oz) = 30g carbs

Adjust based on how much your stomach tolerates during training.

Sodium Targets for Endurance Runs

Maintaining proper sodium levels is crucial for peak performance during long-distance runs. Discover how to calculate and manage your sodium intake to stay energized and avoid dehydration.

Why Sodium?

Sodium helps retain water, regulate fluid balance, and prevent cramping. Sweat rates vary among runners, influencing sodium needs significantly.

Common Sodium Sources

• Salt tablets = 200–300mg sodium per tablet
• Sports drinks = ~250–400mg sodium per 16 oz
• Energy gels (with added sodium) = ~100–200mg sodium

Sweat heavily or run in hot conditions? Opt for higher sodium intake.

Hydration Tips for Endurance Runners

Hydration is more complex than simply drinking water. Overhydrating without replacing electrolytes can lead to imbalances like hyponatremia. Here’s how to stay hydrated:

• Before the Run: Drink 16–24 ounces 2 hours before and 8 ounces 30 minutes before running.
• During the Run: Sip consistently, aiming for 16–24 ounces/hour.
• After the Run: Rehydrate with electrolytes to replenish lost fluids and aid recovery.

Monitor hydration by checking for pale yellow urine and avoiding massive body weight drops (>2%).

Fuel Your Runs Like a Pro

Endurance running requires both strategy and stamina to succeed. Proper fueling is key and can include options like gels, real food, or sports drinks. Finding the right approach can drastically improve your performance and help make even the longest runs feel more achievable.

It's important to experiment with different fueling options during training to see what works best for your body. Every runner is unique, so personalizing your nutrition strategy is essential. For expert guidance, consider consulting a sports nutritionist or dietitian to tailor a plan that suits your goals.

Ready to Elevate Your Running Nutrition?

Unlock more expert insights, tried-and-true tips, and game-changing strategies to fuel your runs and reach your full potential. Subscribe to our newsletter and become part of a passionate community of runners who are chasing their goals every day. Your next personal best starts now—join us today!