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 the 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 exercise. Examples: white rice with chicken, pasta with a 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 sufficient. Beyond that, add electrolytes (mainly sodium) and fast-acting carbs (30 to 60 g/hour). Sports drinks, gels, and fruit chews are convenient options. Drink in small, regular sips, not large quantities at once.

3

Recover within 30 to 60 minutes

After your run, consume a 3:1 carb-to-protein ratio within an hour to replenish glycogen and kick off 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 carb needs vary according to your training phase. During high-volume periods, increase carbs (5 to 7 g/kg). During the tapering phase before a race, reduce volume but maintain carbs to top off 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 fuel in advance, know the course's hydration stations, and schedule your intake every 30 to 45 minutes.

Carb loading explained

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

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

Note: each 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 rate varies 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 over 90 minutes.

Iron and runners

Runners, and particularly female runners, are at an increased risk of iron deficiency. Foot-strike impact destroys a small amount of red blood cells (foot-strike hemolysis), sweating loses iron, and post-effort inflammation temporarily reduces intestinal absorption.

Low ferritin (below 30 ng/mL, even without anemia) can explain persistent fatigue, declining performance, and slow recovery. Have your ferritin levels checked 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 by medical prescription after a blood test.

FoodCraft Tip

TDEE adjusted for running

The FoodCraft TDEE calculator takes activity levels 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 the effort, 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 carbs (glucose + fructose) for optimal absorption. Gels based on maltodextrine and fructose in a 2:1 ratio allow you to absorb up to 90 g of carbs per hour. It's essential to test them in 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 number varies slightly with speed, elevation, and stride efficiency.
How to avoid digestive issues while running?
Avoid excess fiber, fat, and protein in the 3 hours before the race. Train your gut to tolerate carbs during exercise by gradually including them in your long runs. The stomach adapts with practice. Avoid anti-inflammatories (ibuprofen) which increase the risk of digestive problems.

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