Nutrition for Endurance Training

Proper nutrition isn't optional—it's foundational to converting training stress into performance gains. All the training in the world won't produce adaptations if you're not giving your body the fuel it needs to build fitness.

Working with Professionals

Highly recommended: Consult a sports-specific Registered Dietitian (RD) or Certified Sports Nutritionist. General nutrition advice often doesn't account for the unique demands of endurance training. This is particularly important if you're training more than 10 hours per week or preparing for ultra-endurance events.

A sports-specific professional can help you:

  • Calculate your individual energy needs

  • Develop race-day fueling strategies

  • Address specific challenges (GI issues, weight management, dietary restrictions)

  • Optimize recovery nutrition

  • Navigate supplement decisions

Not all nutrition professionals are the same. Look for credentials like RD (Registered Dietitian), RDN (Registered Dietitian Nutritionist), or board certification in sports dietetics (CSSD). General nutritionists may lack the specialized training needed for endurance athletes.

Energy Balance: The Foundation

Low energy availability is one of the most overlooked contributors to poor training adaptations and overtraining. When you consistently consume fewer calories than your body needs for both daily function and training, you:

This constellation of problems is called Relative Energy Deficiency in Sport (RED-S). The IOC consensus statement on RED-S provides comprehensive evidence on these effects.

The bottom line: Don't sabotage your hard work by chronically under-fueling. If you're training hard and losing weight unintentionally, experiencing persistent fatigue, or suffering frequent illness, consult a sports dietitian to assess your energy availability.

Carbohydrate Fueling During Exercise

For workouts longer than 90 minutes, carbohydrate intake becomes increasingly important for maintaining performance.

General Guidelines Based on Exercise Duration

Duration Carbohydrate Intake
45-75 minutes Small amounts (up to 30g/hour) may be beneficial
1-2.5 hours 30-60g per hour
2.5+ hours 60-90g per hour for most athletes
Ultra-endurance (4+ hours) Some elite athletes can utilize up to 120g per hour with proper training

The Science Behind Higher Intakes

The type of carbohydrate matters for higher intakes. At intakes above 60g per hour, combining different carbohydrate types (glucose sources like maltodextrin with fructose) allows higher absorption rates because they use different intestinal transporters.

Single carbohydrate source (glucose only): Maximum absorption ~60g/hour

Multiple transportable carbohydrates (2:1 glucose:fructose): Can achieve 90g/hour absorption

Elite ultra-endurance athletes: With extensive gut training, some can utilize up to 120g/hour

Research shows that higher carbohydrate intakes during ultra-endurance events correlate with better performance outcomes, but this requires systematic training of your digestive system.

Training Your Gut

Your gut needs training too. Start with lower carbohydrate intakes and progressively increase over 4-8+ weeks of training. This "gut training" allows your digestive system to adapt and reduces the risk of GI distress. Learn more about training your gut.

Practical approach to gut training:

  1. Start with your current comfortable intake (perhaps 30-40g/hour)

  2. Gradually increase by 10-15g/hour every 1-2 weeks

  3. Test new intake levels during training, not races

  4. Pay attention to GI comfort and adjust as needed

  5. Build up to your target race intake over 8-12 weeks

Race-Day Nutrition

Nothing new on race day. Test all your race nutrition during training. What works in training is what you use in competition.

Key principles:

  • Practice your race-day fueling strategy during long training sessions

  • Test different products to find what your gut tolerates

  • Have backup options (different flavors, formats) in case of GI issues

  • Account for aid station offerings if you plan to use them

  • Consider temperature—some products become unpalatable in heat

Learn more: MySportScience has excellent evidence-based resources on carbohydrate fueling

Protein: The Overlooked Foundation

Protein is essential for muscle repair, adaptation, and recovery. Many endurance athletes under-consume protein relative to their needs, focusing too heavily on carbohydrates at protein's expense.

Evidence-Based Protein Recommendations

Key recommendations from the International Society of Sports Nutrition:

Daily intake: 1.4-2.0g protein per kg body weight for most exercising individuals

  • Example: A 70kg (154lb) athlete needs 98-140g protein per day

  • Higher-volume training pushes you toward the upper end of this range

Per-meal dosing: 0.25g per kg body weight, or approximately 20-40g per serving

  • Example: That same 70kg athlete should aim for ~17-25g protein per meal

  • This amount maximizes muscle protein synthesis per feeding

Distribution: Consume protein every 3-4 hours throughout the day for optimal muscle protein synthesis

  • Four meals per day with 25-35g protein each is better than two large meals

  • Consistent distribution maintains elevated muscle protein synthesis throughout the day

Timing consideration: While the "anabolic window" is less critical than once thought, consuming protein relatively soon after training (within a few hours) supports recovery

  • Post-workout protein isn't magic, but it's practical

  • If you train in the morning and won't eat for 6 hours, post-workout protein matters more

  • If you train before dinner, your normal meal timing is fine

Before bed: 30-40g of casein protein before sleep supports overnight muscle protein synthesis

  • Slow-digesting protein provides sustained amino acid availability

  • Greek yogurt, cottage cheese, or casein supplements work well

Protein for Masters Athletes

For masters athletes (typically 40+): Protein requirements may be higher than for younger athletes due to anabolic resistance—the reduced muscle protein synthesis response to protein intake and exercise. This article discusses protein needs for older athletes.

Masters athletes should:

  • Aim for the higher end of protein recommendations (1.8-2.0g/kg)

  • Prioritize protein distribution throughout the day

  • Consider slightly higher per-meal doses (30-40g vs. 20-30g)

  • Emphasize leucine-rich protein sources (dairy, eggs, meat)

Practical Protein Sources

High-quality protein sources (complete amino acid profiles):

  • Lean meats (chicken, turkey, lean beef)

  • Fish and seafood

  • Eggs and egg whites

  • Dairy (Greek yogurt, cottage cheese, milk)

  • Whey and casein protein supplements

  • Soy products (tofu, tempeh, edamame)

For plant-based athletes:

  • Combine complementary protein sources (grains + legumes)

  • Consider higher total protein intake (upper end of recommendations)

  • Leucine-fortified plant protein supplements can be beneficial

  • Soy and pea protein isolates are complete proteins

Hydration and Electrolytes

Stay hydrated. Dehydration impairs both performance and recovery. General guidelines suggest drinking to thirst during exercise, with sodium intake of 300-600mg per hour for most athletes during prolonged exercise. Individual needs vary significantly—consider getting a sweat test to dial in your specific requirements. Precision Hydration offers sweat testing.

Understanding Individual Sweat Rates

Sweat rates vary dramatically between athletes:

  • Low sweaters: 0.5-0.8 L/hour

  • Average sweaters: 0.8-1.2 L/hour

  • High sweaters: 1.5-2.5+ L/hour

Sodium concentration in sweat also varies:

  • Low: 200-500 mg/L

  • Average: 500-1000 mg/L

  • High: 1000-2000+ mg/L

Why this matters: A high-volume, high-sodium sweater might lose 2000+ mg sodium per hour, while a low-volume, low-sodium sweater might lose only 200mg. Generic advice doesn't work for everyone.

Practical Hydration Guidelines

During exercise:

  • Drink to thirst as a starting point

  • For efforts over 2 hours, consider planned hydration rather than thirst alone

  • Monitor urine color (pale yellow is ideal)

  • Weigh yourself pre/post long sessions to understand sweat losses

  • Replace 125-150% of fluid losses post-exercise (you continue sweating after you stop)

Sodium intake during exercise:

  • Start with 300-600mg/hour for moderate sweaters

  • Increase to 800-1200mg/hour for heavy sweaters or hot conditions

  • Sources: sports drinks, salt tabs, salted foods at aid stations

  • Consider caffeine + sodium combinations for ultra-endurance

Signs you may need more sodium:

  • Muscle cramping late in long efforts

  • Feeling bloated despite drinking

  • Headaches during/after exercise

  • Rings feeling tight on hands

Recovery Nutrition

Post-exercise nutrition goals:

  1. Replenish glycogen stores

  2. Provide protein for muscle repair

  3. Rehydrate and replace electrolytes

The classic recommendation: 3:1 or 4:1 carbohydrate to protein ratio within 30-60 minutes post-exercise

  • Example: 60g carbs + 15-20g protein

  • This can be a recovery drink, chocolate milk, or a meal

Reality check: If you're eating regular meals every 3-4 hours, the timing is less critical. The "anabolic window" matters most when:

  • Next meal is 4+ hours away

  • Training twice per day

  • Racing multiple days in a row

  • Training in a fasted state

Focus on total daily intake over timing minutiae. Eating sufficient total protein and carbohydrates matters more than precise post-workout timing for most athletes.

Common Nutrition Pitfalls

Mistake #1: Carb-loading only before races

  • Practice your loading protocol during training

  • Some athletes experience GI distress with sudden carb increases

  • Test timing, amounts, and food choices before race week

Mistake #2: Neglecting protein for recovery

  • Endurance athletes often over-emphasize carbs, under-emphasize protein

  • Both are essential—don't sacrifice one for the other

Mistake #3: Training the gut only with race nutrition

  • Your gut needs to adapt to processing carbs during exercise

  • Practice high-carb intake even with products you won't race with

Mistake #4: Copying what works for others

  • Individual variation in sweat rate, GI tolerance, and metabolism is enormous

  • Find what works for YOUR body through systematic testing

Mistake #5: Chronic low energy availability

  • "Train low, race high" has limits

  • Persistent under-fueling undermines adaptation and health

Additional Resources

Comprehensive nutrition science:

Specific topics:

Key Sources

The evidence-based recommendations in this guide draw from:

Individual needs vary significantly. These guidelines provide evidence-based starting points for experimentation and personalization.