Marathon Nutrition: What to Eat Before, During, and After
A practical marathon fueling guide. Carb loading, race-day breakfast, gel timing, hydration strategy, and recovery nutrition.
You can train perfectly for 16 weeks and blow up your marathon with bad nutrition on race day. Fueling is not optional for the marathon. Your body stores about 2,000 calories of glycogen, and you'll burn 2,800-3,500 depending on your weight and pace. The math doesn't add up without eating during the race.
The week before: carb loading
Carb loading isn't about stuffing yourself with pasta the night before. It's about gradually increasing your carbohydrate percentage to 65-70% of total calories over the final 3 days while keeping total calories steady. Your muscles can store about 20% more glycogen when properly loaded.
Good carb sources: White rice, pasta, bread, potatoes, bananas, oatmeal, pretzels. Avoid high-fiber carbs (beans, bran) and anything new. Race week is not the time to experiment.
Race morning: 3 hours before the start
Eat 2-4 grams of carbohydrate per kilogram of body weight. For a 70kg runner, that's 140-280g of carbs. Example: a large bowl of oatmeal with banana and honey, plus a sports drink. This tops off your liver glycogen after the overnight fast.
Avoid: High fat, high fiber, dairy (for many people), and anything you haven't eaten before a long run.
During the race: the fueling plan
Start fueling at 30-45 minutes, then every 25-35 minutes. Target 30-60g of carbs per hour for races under 3 hours, and 60-90g per hour for slower finishers who are out there longer.
One gel = about 25g of carbs. So you need 5-8 gels for a marathon. Take them with water, not sports drink (double sugar can cause stomach distress).
Use the nutrition calculator to build a personalized fueling schedule based on your weight, pace, and expected finish time. It calculates exactly when to take each gel and how much fluid you need.
Hydration
Drink 400-800ml per hour depending on temperature. In cool conditions (under 15C), aim for the low end. In heat (over 25C), the high end. Don't over-hydrate — hyponatremia (low sodium) is more dangerous than mild dehydration.
Take in sodium too: 300-600mg per hour. Most sports drinks provide this. If you're using water + gels, consider salt tablets.
After the race: recovery
Within 30 minutes of finishing: 1-1.5g of carbs per kg plus 20-30g of protein. Chocolate milk is the classic recovery drink. A bagel with peanut butter and a banana works too. Then eat a full meal within 2 hours.
Check how your body weight affects your fueling needs with the weight impact calculator.