Nutrition for Running

Running is one of the most energy-demanding sports. A marathon burns about 2,500 to 3,500 kcal, and even a 10 km run heavily taxes your glycogen stores. Properly fueling your body before, during, and after a run makes the difference between performance and hitting the wall.

Steps

1

Fuel up before the run

Eat a meal high in carbs and low in fiber and fat 2 to 3 hours before the effort. Examples: white rice with chicken, pasta with light sauce, or porridge with banana. For a short morning run (less than 60 min), a banana or a slice of bread with honey is enough.

2

Hydrate during the effort

For efforts under 60 minutes, water alone is enough. Beyond that, add electrolytes (primarily sodium) and fast carbs (30 to 60 g/hour). Sports drinks, gels, and fruit pastes are convenient options. Drink in regular small sips, not large quantities all at once.

3

Recover within 30 to 60 minutes

After the run, consume a 3:1 carb-to-protein ratio within the hour to replenish glycogen and kickstart muscle repair. Examples: chocolate milk, yogurt with granola and fruit, or rice with chicken. Continue to hydrate well in the following hours.

4

Periodize your nutrition

Your calorie and carbohydrate needs vary depending on your training phase. During high-volume periods, increase carbs (5 to 7 g/kg). During the tapering phase before a competition, reduce volume but maintain carbs to top up glycogen stores.

5

Plan your race day nutrition

Never try a new food or gel on race day. All your race nutrition choices should have been tested during training. Prepare your fueling in advance, know the course's aid stations, and schedule your intake every 30 to 45 min.

Carb loading explained

Carb loading (glycogen supercompensation) involves increasing your muscle glycogen stores before an event lasting more than 90 min. The modern protocol is simple: 3 days before the race, increase carbohydrates to 8 to 10 g/kg while reducing training volume.

Normal glycogen stores are around 400 to 500 g (1,600 to 2,000 kcal). After successful carb loading, they can reach 700 to 800 g. This difference pushes back the famous marathon "wall" by a few kilometers and maintains a higher intensity.

Note: every gram of glycogen stores 3 g of water. You will gain 1 to 2 kg during carb loading, which is normal and desirable. This extra weight is lost during the race. Don't panic when you see the scale go up the day before the event.

Hydration during long runs

Dehydration of more than 2% of body weight significantly degrades running performance: increased heart rate, decreased blood flow, and reduced thermoregulation. For a 70 kg runner, this represents a 1.4 kg fluid loss.

Sweat rates vary from 0.5 to 2 liters per hour depending on temperature, humidity, and intensity. Weigh yourself before and after a training run to estimate your sweat rate and calibrate your hydration strategy.

Hyponatremia (too low sodium levels) is the opposite danger: drinking too much pure water without sodium during prolonged effort dilutes blood sodium. This is why sports drinks containing sodium (300-700 mg/L) are preferable to pure water for efforts lasting more than 90 min.

Iron and runners

Runners, and especially female runners, are at increased risk of iron deficiency. Foot impact on the ground destroys a small amount of red blood cells (foot strike hemolysis), sweat carries away iron, and post-exercise inflammation temporarily reduces intestinal absorption.

Low ferritin (below 30 ng/mL, even without anemia) can explain persistent fatigue, declining performance, and slow recovery. Get your ferritin levels tested at least once a year if you run regularly.

To maintain adequate iron stores: include red meat 2 to 3 times a week, or combine plant sources (lentils, spinach) with vitamin C. Avoid coffee and tea within an hour of an iron-rich meal. Supplementation should only be done with a medical prescription following a blood test.

FoodCraft Tip

Adjusted TDEE for running

FoodCraft's TDEE calculator takes activity level into account and can be set for endurance athletes. Use it to estimate your calorie needs during intense training phases and adjust your diet accordingly to avoid relative energy deficiency.

Frequently Asked Questions

Should I run fasted to burn more fat?
Running fasted increases the percentage of fat oxidized during exercise, but total fat loss over 24 hours is not higher. For short, easy runs, it's a viable option. For intense or long sessions, fueling beforehand improves performance and training quality.
Which energy gel should I choose?
Choose a gel containing 20 to 30 g of mixed carbohydrates (glucose + fructose) for optimal absorption. Maltodextrin and fructose-based gels in a 2:1 ratio allow you to absorb up to 90 g of carbohydrates per hour. You must test them during training to check your digestive tolerance.
How many calories do you burn while running?
On average, running burns about 1 kcal per kg of body weight per kilometer. A 75 kg runner therefore burns about 75 kcal per kilometer, or 750 kcal for a 10 km. This figure varies slightly with speed, elevation, and stride efficiency.
How can I avoid digestive issues while racing?
Avoid excess fiber, fats, and protein in the 3 hours before the race. Train your gut to tolerate carbohydrates during exercise by gradually including them in your long runs. The stomach adapts with practice. Avoid anti-inflammatory drugs (ibuprofen) which increase the risk of digestive problems.

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