Calorie Intake for Marathon: How Much Fuel Do You Really Need?

If you’re gearing up for a marathon, the biggest mistake you can make is ignoring your food. Your body will burn a lot of energy, and without the right amount of calories, you’ll feel sluggish, hit the wall, or recover slowly. Below is a simple guide that shows exactly how many calories to aim for, what foods work best, and how to tweak the plan to fit your own body.

How Many Calories Should You Eat?

First, figure out your baseline: multiply your weight (in pounds) by 15‑18 calories for a light training day. For a 150‑lb runner, that’s roughly 2,250‑2,700 calories. On long‑run days (10‑20 miles) add 100‑150 calories for every mile you cover beyond your normal workout. A 15‑mile long run could push the total to about 3,500‑4,000 calories.

Carbohydrates are king during marathon prep. Aim for 55‑65% of your total calories to come from carbs. That means if you’re eating 3,500 calories, about 1,925‑2,275 of those should be carbs – roughly 480‑570 grams per day. Protein should sit at 15‑20% (about 130‑175 grams) to repair muscle, while fats fill the remaining 20‑30% for hormone balance and long‑lasting energy.

Don’t forget the timing. Eat a carb‑rich snack (like a banana or a granola bar) 30‑60 minutes before a run. During runs longer than 90 minutes, aim for 30‑60 grams of carbs per hour – think sports gels, dried fruit, or a small sandwich. After the race, grab a 3:1 carb‑to‑protein combo (like chocolate milk) within 30 minutes to kick‑start recovery.

Practical Tips to Fine‑Tune Your Marathon Diet

1. Track your intake. Use a free app to log meals for a week. You’ll see where you’re over‑ or under‑eating and can adjust on the fly.

2. Choose low‑fiber foods before long runs. Too much fiber can cause gut issues mid‑race. Switch to white rice, plain pasta, or a bagel the night before.

3. Stay hydrated but avoid over‑drinking. Aim for 500‑700 ml of water or a sports drink per hour of running. Your urine should be a light straw color – that’s the sweet spot.

4. Test your race‑day nutrition in training. Never try a new energy gel or a weird breakfast on race morning. Use your long runs to see how your stomach reacts.

5. Adjust for weather. On hot days, you’ll sweat more and need extra electrolytes. A pinch of sea salt in your water or an electrolyte tablet can keep cramps at bay.

6. Listen to your body. Feeling constantly fatigued? You might be under‑fueling. Notice cravings for carbs after a run – that’s a sign your glycogen stores are depleted.

Putting these steps together creates a flexible, personalized calorie plan that keeps your energy steady from the first training jog to the finish line. Remember, the goal isn’t just to hit a number on a calculator; it’s to feel strong, stay focused, and finish the marathon feeling proud.

Got a favorite pre‑run snack or an on‑the‑go fuel hack? Share it in the comments and help other runners nail their calorie intake for marathon success.