Everything you need to know about fuelling your first ultra marathon

So you have decided to tackle an ultra marathon and now you are wondering how on earth people stay moving for twelve or twenty-four hours without collapsing. The secret is that trail running is basically an eating contest where you happen to do a lot of jogging. When you are covering distances between 40 and 160 kilometres, your body is burning through energy much faster than it can replace it from its internal stores. Think of your body like a car with a tiny fuel tank but a massive trunk full of spare gas cans that you can’t quite reach while driving. To keep the engine running, you have to constantly pour a little bit of fuel into the tank as you go. That fuel primarily comes from carbohydrates because they are the body’s preferred and most efficient source of energy during high-intensity efforts. Scientifically speaking, every single gram of carbohydrate you eat provides about four calories of energy. If you aim for the standard recommendation of sixty to ninety grams of carbohydrates per hour, you are effectively taking in 240 to 360 calories every sixty minutes. This is crucial because your brain and muscles run on glucose, and once you run out of that stored glycogen in your liver and muscles, a state runners call bonking, your pace will plummet and your mood will follow it into the dirt.

Recent insights from the pros show that this number can change depending on how hard you are running. In a high-intensity 100-kilometer race, some elite athletes push as much as 110 grams of carbs per hour to maintain their speed. However, as the distance gets longer and the intensity drops, aiming for a consistent 60 grams per hour is often more realistic and sustainable for the gut. A common tool for this is the energy gel, which is essentially a small plastic pouch filled with a very thick, gooey syrup made of concentrated sugar and electrolytes. They are designed to be swallowed quickly without much chewing, which is helpful when you are breathing hard. Many runners find that relying only on gels gets old really fast, so they use high-carb liquid mixes in their water bottles as well. These are powders you stir into your water that turn your hydration into a constant stream of calories. The best way to use them is in conjunction: you might sip on your liquid calories throughout the hour to get about forty grams of carbs and then eat one gel at the forty-five-minute mark to hit your total target. This strategy prevents your blood sugar from spiking and crashing while keeping your digestion moving smoothly.

You also have to be careful in different weather conditions. If it is a cold race, you might not feel thirsty, but if all your fuel is in your water bottle, you might stop eating because you stopped drinking. This is why having a backup plan with gels and real food is vital. Speaking of real food, pros like Courtney Dauwalter often switch to things like salted potatoes, pierogies, or quesadillas later in a race. These provide a bit of protein and fat, which can help settle a sour stomach and provide a slower-burning energy source when you have been running for ten hours and can no longer stand the taste of strawberry-flavoured syrup.

Beyond just calories, you need to manage your mental state and long-term recovery. For mental clarity, many runners use caffeine, but the trick is to treat it like staying tipsy rather than getting drunk. Instead of one massive dose that leads to a crash, taking small, frequent doses of 50 to 100 milligrams every three hours helps you fight off fatigue without wrecking your stomach. Some athletes also look into supplements like creatine to help with the brain fog caused by sleep deprivation, though you have to remember that creatine isn't a race-day fix; it requires a loading phase of about a month during your training to actually work.

Finally, once you cross that finish line, the fuelling process enters its most important phase. You have a golden window of about thirty to sixty minutes where your muscles are like sponges. You should aim for a snack or drink with a three-to-one ratio of carbs to protein. The carbs replenish the energy you just torched, and the protein starts repairing the microscopic tears in your muscles. Whether it is a recovery shake or a big bowl of pasta with chicken, getting that fuel in early is the difference between walking normally the next day or needing to crawl down the stairs backward. Just remember the golden rule: never try anything new on race day. Your gut needs to be trained to handle food under stress just as much as your legs need to be trained to handle the miles.