Eat like an elite: the science behind marathon nutrition

Quick guide: the elite fuelling formula

• Before the race: 10–12 g of carbs per kg of bodyweight for 36–48 hours

• During the race: 75–90 g of carbs per hour (3–4 gels)

• Fluids: keep weight loss under 2–3%

• Caffeine: 3–6 mg per kg of bodyweight, pre- or mid-race

You probably can’t train exactly like an elite marathon runner. You have a job, a life, and probably less time to nap between runs. But there is one part of their routine you can copy directly: nutrition.

When it comes to marathon performance, what you eat and drink before and during the race makes a measurable difference. A major review in the International Journal of Sport Nutrition and Exercise Metabolism pulled together dozens of studies on elite endurance runners to find out exactly what works.

The results are surprisingly clear.

Carb loading: the science behind the pasta party

The advice before a marathon is simple: fill your muscles with glycogen, your body’s main fuel source for endurance exercise.

The review recommends ten to twelve grams of carbohydrate per kilogram of body weight per day, for about 36 to 48 hours before your race.

So, if you weigh 70 kilograms, that’s around 700 to 840 grams of carbohydrate per day. In real terms, roughly a kilo of cooked pasta, plus bread, fruit, and perhaps and a sports drink on top.

During the race: train your gut like the elites

While running, the advice is seventy-five to ninety grams of carbohydrate per hour — about three to four energy gels every hour. This is relevant for races over 90-120 minutes in duration.

That sounds like a lot, and for many runners it is. If you have ever tried that many gels in a race without practice, you’ll know your stomach might not thank you. Which is why elite runners spend months training their gut to handle it.

This is one of the biggest takeaways for recreational runners. Just like you train your muscles, you can train your digestive system to tolerate more carbohydrate. Start with smaller doses during long runs and build up gradually.

If your goal is to finish strong, this level of fuelling helps you maintain pace rather than simply delaying the fade.

Fluids and caffeine: small changes, big impact

The review also looked at hydration and caffeine.

For fluids, the aim is to keep your weight loss below two to three per cent during the marathon. You don’t need to replace every drop of sweat, but you want to avoid excessive dehydration.

Caffeine, meanwhile, has consistent evidence for improving endurance. The recommendation is three to six milligrams per kilogram of body weight, taken before or during the race. For a 70 kilogram runner, that’s roughly the caffeine in three to five espressos.

A less-known trick mentioned in the paper is carbohydrate mouth rinsing. Swilling a carb drink or gel in your mouth and spitting it out can activate brain receptors linked to endurance — a clever hack for runners with sensitive stomachs.

What we can learn from Kenyan runners

The review also explored the eating habits of Kenyan marathoners. Interestingly, their diet is high in carbohydrates but low in meat and animal fat, and they often train in a slight caloric deficit during heavy training blocks.

This pattern might not be perfect for everyone, but it highlights that performance isn’t about exotic supplements or constant protein shakes. It’s about fuelling well, consistently, with simple foods. Don’t underestimate the importance of carbohydrates.

The bigger picture

This study doesn’t just offer guidelines; it’s a reminder that the best performance strategies are practical. You don’t need a lab or a team of scientists to apply them.

Carbohydrate loading, hydration, caffeine — these are things every runner can control. The difference between finishing strong and hitting the wall often comes down to whether you’ve practised your nutrition as carefully as your pacing.

So, if you want to run like an elite, start with your fuelling plan.