Running Nutrition & Fueling: From Training to Race Day - 2025 Guide

Fuel smarter from training to race day. Practical nutrition, hydration, carb-loading, and on-course fueling plans for 5K to ultramarathon runners.

Running gets you to the start line. Smart fueling gets you to the finish feeling strong. Whether you’re chasing a 5K PR or toeing the line for your first ultramarathon, dialing in nutrition and hydration is the quiet advantage that changes race day from a grind to a performance.

This guide breaks down daily eating, pre-race preparation, and during-race fueling into practical steps you can test in training and execute with confidence on race day. We’ll also show you how to use RaceThere’s event discovery tools to find races with the on-course support that fits your plan.

Core principles that actually matter

• Carbs are your race-day fuel. Glycogen stores are limited; most runners have 90–120 minutes of strong, glycogen-fueled running before pace fades without added carbs.
• Hydration supports performance, but both under- and over-drinking hurt. Aim to replace a portion of sweat loss, not all of it.
• Sodium matters for many runners, especially in heat or if you’re salty sweaters. Pair sodium with fluids and carbs.
• Your gut is trainable. Practice your race fueling at realistic intensities to reduce GI distress.
• Keep it personal. Body size, sweat rate, and pace all influence needs. Use the ranges below as starting points, then refine.

Daily nutrition for runners (the base you build on)

You don’t need a perfect diet; you need a consistent one that supports training load, recovery, and overall health.

• Carbohydrates: 5–7 g/kg/day for moderate training, 7–10 g/kg/day for heavy blocks. Prioritize whole grains, fruit, potatoes, and rice.
• Protein: 1.4–1.8 g/kg/day, distributed across 3–5 feedings. Include 20–35 g protein within 1–2 hours after key runs.
• Fats: 20–35% of daily calories from sources like olive oil, nuts, avocado, and fatty fish.
• Micronutrients that matter:
  • Iron (especially for menstruating athletes). Pair iron-rich foods with vitamin C.
  • Vitamin D and calcium for bone health.
  • Magnesium and potassium for muscle function.
• Everyday hydration: Sip fluids through the day; your urine should be pale straw color. Add a pinch of electrolytes when it’s hot or your training volume climbs.
• Caffeine: Effective dose for performance is typically 1–3 mg/kg (up to ~400 mg/day total from all sources). Test your timing and dose in training.

Pro tip: Keep a short list of “easy wins” meals you can throw together on busy days—oats with banana and peanut butter; eggs, toast, and fruit; rice, beans, greens, and salsa.

Pre-run fueling (from the everyday jog to key workouts)

Match fuel to the session intent.

• 3–4 hours before a long run or hard workout: Balanced, carb-forward meal (~2–3 g/kg carbs), moderate protein, lower fiber/fat. Example: rice bowl with lean protein and cooked vegetables.
• 60–90 minutes before: 30–60 g carbs from easy options like a bagel with honey, a banana, or a sports drink. Keep fiber and fats low.
• 10–20 minutes before: Optional top-off of 20–30 g fast carbs (gel or drink) if the session is intense.
• Avoid: New foods, high-fiber choices, or heavy fats right before running if you’re prone to GI issues.

Race week and carb-loading (without the bloat)

Carb-loading boosts glycogen for events >90 minutes. Keep it simple:

• Taper volume, keep easy strides to stay sharp.
• 36–48 hours pre-race: Emphasize carbs. Target 7–10 g/kg/day for marathons and long trail races; 5–7 g/kg/day for half marathons. Spread across meals and snacks.
• Keep protein and fats moderate; salt food to taste.
• Choose low-fiber, familiar carbs to minimize GI load (white rice, potatoes, pasta, bread, ripe fruit).
• Hydration: Sip regularly, include electrolytes if you’re a heavy/salty sweater. Avoid aggressive overdrinking.

Morning-of checklist:

• Eat a known pre-race meal 2–3 hours before (1–3 g/kg carbs, low fiber/fat).
• Top off with a gel or sports drink 10–15 minutes before the gun if it’s worked in training.
• If you use caffeine, take your planned dose 30–60 minutes pre-start.

During-race fueling by distance

These are starting ranges you’ll refine in training. Faster runners often need the same hourly targets but may take fewer total carbs due to shorter race time.

• 5K

  • Carbs: Optional. If pre-fueled, most don’t need on-course carbs.
  • Fluids: Sips as needed, especially in heat.
  • Caffeine: If you tolerate it, pre-race dose only.

• 10K

  • Carbs: Optional to 20–30 g mid-race if >45–50 minutes.
  • Fluids: A few sips at one aid station; more in heat.
  • Caffeine: Pre-race dose; small on-course top-up if >50–60 minutes and you’ve practiced it.

• Half Marathon

  • Carbs: 30–60 g/hour. Many do well with 1 gel every 30–40 minutes.
  • Fluids: 400–700 ml/hour depending on sweat rate and weather.
  • Sodium: 300–600 mg/hour for most; higher if very salty or in heat.

• Marathon

  • Carbs: 60–90 g/hour using multiple carb sources (glucose + fructose blends). Think 1 gel every 20–25 minutes or a mix of gels/chews/drink.
  • Fluids: 500–800 ml/hour, adjusted by sweat rate.
  • Sodium: 500–800+ mg/hour. Heavier sweaters may need 800–1,000 mg/hour in heat.
  • Caffeine: 1–3 mg/kg total split pre-race and during. Avoid exceeding your practiced dose.

• Ultramarathon (time and terrain drive needs)

  • Carbs: 60–120 g/hour. Many alternate sports fuels with “real” foods (rice balls, soft potatoes, PB&J, broth with noodles) to avoid palate fatigue.
  • Fluids: 500–900 ml/hour on average; higher in heat but avoid chugging.
  • Sodium: 600–1,000+ mg/hour depending on sweat concentration and conditions.
  • Strategy: Eat early and often, even when you don’t feel hungry. Pace and gut comfort rule the day.

How to choose your fuel format

• Gels and chews: Compact and easy to count. Always chase gels with water unless it’s a gel-plus-electrolyte blend designed for use without water.
• Drink mixes: Convenient for steady drip fueling; ensure aid stations provide compatible fluids or carry your own.
• Solids: Better for ultras and hiking sections. Keep pieces small and easy to chew.
• Multiple transportable carbs: Look for products with glucose and fructose to push toward the higher end of the hourly carb range without GI overload.

Hydration and electrolytes without the guesswork

Sweat rate and sodium concentration vary widely. Here’s a practical testing approach.

• Simple sweat-rate test:
  1. Weigh yourself nude right before a run.
  2. Run 60 minutes at typical race intensity, tracking fluids consumed.
  3. Towel off and weigh nude after.
  4. Each 1 lb (0.45 kg) lost ≈ 16 oz (473 ml) sweat. Sweat rate ≈ (weight loss in oz + fluid consumed in oz) per hour.
• Fluid target on race day: Replace 50–80% of hourly sweat loss. You don’t need to replace 100%.
• Sodium target: Start with 300–600 mg/hour for cool conditions and 600–1,000 mg/hour in heat or if you see salt crusts on clothing/skin.
• Signs you need more fluid/electrolyte: Dizziness, mounting thirst, hot/cold chills, progressively slower pace unrelated to effort.
• Signs you’re overdoing fluid: Sloshing stomach, frequent clear urination during the race, hand swelling, headache. Overdrinking can cause hyponatremia—pair fluids with sodium and listen to thirst cues.

Preloading? A modest electrolyte-rich drink the evening before and with breakfast can help. Avoid aggressive “water loading.”

Train your gut like you train your legs

GI issues are often a training problem, not a race-day curse.

• Progression: Start at 30 g carbs/hour on long runs and add ~10–15 g/hour each week until you reach your race target.
• Intensity matters: Practice fueling at goal race pace, not only on easy long runs.
• Consistency: Eat on a clock (every 20–30 minutes). Don’t wait until you “feel” like it.
• Texture variety: Mix gels, chews, and drink mix to reduce flavor fatigue.
• Low-fiber day-before: If you’re GI-sensitive, reduce roughage 12–24 hours pre-race.
• Caution with meds: Anti-diarrheals and NSAIDs can have side effects; talk with a healthcare professional before race-day use.

Special considerations

• Heat and humidity: Increase fluids and sodium; lower early pace slightly to protect the gut and allow fueling to work.
• Altitude: Hydration needs often rise; appetite may drop. Set timers to eat.
• Menstrual cycle: Track cycles and symptoms. Some runners need slightly more carbs and electrolytes during the luteal phase. Prioritize iron status.
• Vegetarian/vegan: Watch iron (heme vs. non-heme), B12, calcium, and protein distribution. Pair beans and grains for complete amino acids.
• Low-FODMAP approach: If you get mid-run cramping/bloating, experiment with a low-FODMAP pattern in the 24 hours pre-race while still meeting carb goals.

Sample, practical fueling plans

Use these as templates. Adjust for body size, pace, and weather—and practice before race day.

10K (50–65 minutes)

• Breakfast (2–3 hours pre): Toast with honey + half banana + 250–350 ml sports drink.
• 10 minutes pre: Optional 20–25 g carb gel if you’ve tested it.
• During: 2–3 quick sips of water or sports drink at one aid station.

Half Marathon (1:40–2:15)

• Breakfast: Bagel with jam + small yogurt or egg whites + 300–500 ml electrolyte drink.
• 15 minutes pre: 1 gel (20–25 g carbs) + a few sips water.
• During:
  • 1 gel every 35–40 minutes (3 total for a 2:00 finish).
  • 400–600 ml/hour fluids split across aid stations.
  • 300–600 mg sodium/hour via drink mix plus 1 salt capsule if needed in heat.

Marathon (3:20–4:30)

• Breakfast: White rice with soy sauce + scrambled eggs; or oatmeal with maple syrup and a banana + 500 ml electrolyte drink.
• 10 minutes pre: 1 gel.
• During:
  • 60–90 g carbs/hour via 1 gel every 20–25 minutes plus sips of sports drink, or a steady drink-mix plan in soft flasks.
  • 500–800 ml/hour fluids; adjust based on your sweat-rate test.
  • 500–800+ mg sodium/hour. Consider one higher-sodium bottle early if it’s hot.
  • Caffeine: If tolerated, 50–100 mg at 60–90 minutes, then again at 150–180 minutes.

50K Trail (6–8 hours, rolling terrain)

• Breakfast: Low-fiber carb focus (pancakes + syrup + eggs) + 500 ml electrolyte drink.
• During:
  • 60–90 g carbs/hour (mix gels/chews/drink mix with small real foods like pretzels, rice balls, boiled potatoes with salt).
  • 600–900 ml/hour fluids depending on heat and climbing.
  • 600–1,000 mg sodium/hour, using both drink mix and salt tabs.
  • Use aid stations to swap textures and keep appetite up; carry a “backup” gel for missed stations.

Race-day logistics most runners overlook

• Map the course aid: On your RaceThere race page, check where water and sports drink are offered. Plan gel timing to match those tables.
• Carrying strategy: Pair a waist belt or vest with soft flasks if aid stations are sparse. Practice grabbing cups on the run; pinch and sip.
• Label your gels: Use a marker for timing (e.g., 6, 12, 18 miles) so you don’t have to think.
• Backup plans: If a gel drops, the next aid station should cover you with sports drink. Don’t panic—adjust and keep moving.
• Drop bags (trail/ultra): Pack extra socks, a savory option, caffeine backup, and weather-specific items.

Common mistakes and simple fixes

• Mistake: “I’ll eat when I’m hungry.” Fix: Set a timer and fuel proactively every 20–30 minutes.
• Mistake: All water, no salt, in the heat. Fix: Add 300–600 mg sodium/hour minimum; more if you’re a heavy sweater.
• Mistake: Trying new products on race day. Fix: Taste-test and stomach-test everything in training.
• Mistake: Front-loading carbs and then forgetting late. Fix: Evenly pace intake; late-race gels still help.
• Mistake: Chasing every gel with sports drink. Fix: Alternate gels with water unless product directions say otherwise.

Quick calculators you can use today

1. Carb target per hour

• Half marathon: 30–60 g/hour
• Marathon: 60–90 g/hour
• Ultra: 60–120 g/hour Choose a number, then divide by your chosen product size to set your every-20–30-minute schedule.

2. Sweat rate (home test)

• Sweat rate (ml/h) ≈ [weight loss (kg) × 1,000] + fluids consumed (ml)
• Replace 50–80% on race day.

3. Sodium target

• Cool weather: 300–600 mg/h
• Hot/humid or salty sweater: 600–1,000+ mg/h

Write these on your bib or wrist tape for an easy, race-legal cheat sheet.

Integrate your fueling with gear that works

• Carrying fluids: Handhelds, waist belts, and vests each have pros and cons. See RaceThere’s Hydration Systems Guide for fit and capacity tips.
• Bottles vs. bladders: Bottles make dosing easier with aid stations; bladders shine on long, unsupported stretches.
• Shoes matter too: If your race involves trails, match your fueling plan to the time you’ll spend hiking vs. running. Our Running Shoes Guide can help you choose traction and cushioning for the terrain.

Building your plan in four steps

1. Choose targets

• Pick hourly carbs, fluid, and sodium from the ranges above.

2. Select products

• Two to three formats (e.g., gel + drink mix + chews) prevent flavor fatigue.

3. Practice under stress

• Use at least three long runs at goal intensity with your full plan. Adjust based on stomach comfort and perceived energy.

4. Match your race

• Use RaceThere to find races with the aid setup you prefer—cup-free events, specific sports drink brands, or frequent aid for warmer climates. Filter by distance, terrain, and event features to make your plan easy to execute.

The bottom line

Fueling isn’t mysterious. Set simple targets, practice them, and pick races where your plan is easy to execute. RaceThere can help you find those events—then your nutrition strategy will carry you from confident start to strong finish.

Next step: Choose your goal race on RaceThere, note the course aid and weather trends, and build a two-run “dress rehearsal” week to lock in your fueling. When training meets a smart plan, race day feels a whole lot more fun.