What to eat before a race: what, how much, and when

On race morning, most people improvise: a bit of bread, a coffee, a gel "just in case." That's where the trouble starts: a heavy stomach, empty legs, and a gut that protests at kilometer 8 (mile 5).

Sports science bodies give benchmarks in grams of carbs per kilo of body weight. Here is how to read them based on your race length, and how to test them before race day.

What this meal does

For a race longer than an hour, your main fuel is the carbs your body has stored. The pre-race meal tops up those reserves before the start. It matters most when you start in the morning, after a night without eating.

The benchmarks below are for efforts longer than 60 minutes. They don't apply as-is to a 10 km (6.2 miles) race or any shorter distance, and the carb load described below isn't meant for you in that case. They're expressed in g/kg, so they scale to your body size.

The days before: normalize or load

The 2019 consensus from the International Association of Athletics Federations separates by distance. The numerical examples are for 70 kg.

A "low residue" diet limits foods that leave fiber in the gut. These amounts are large: 700 g of carbs is far more than your usual plate of pasta or rice. Spread them across the day, in meals and snacks. They're easier to digest than one huge plate.

In France, a page from the French Athletics Federation describes a different approach, called "dissociated": about 2.5 days on limited carbs to deplete glycogen, then 2.5 days rich in slow carbs, with a return to normal eating the day before. It differs from the 2019 consensus. Both exist, and no source in this file compares them.

Training for your first half marathon or your first marathon? The half marathon and marathon plans explain how to organize the weeks before.

The pre-race meal: how much, when, and what

How much. For an effort longer than 60 minutes, the benchmark is 1 to 4 g of carbs per kg. At 60 kg, that's 60 to 240 g. At 70 kg, it's 70 to 280 g.

When. The International Association of Athletics Federations consensus and the joint American-Canadian position (ACSM, Academy of Nutrition and Dietetics, Dietitians of Canada) agree: 1 to 4 hours before the start. The DGSP narrows this to 2 to 3 hours. For a 9:00 a.m. race, a meal between 6:00 and 7:00 a.m. fits both.

What. The consensus recommends cutting fat, fiber, and protein, depending on your risk of digestive problems. White bread, rice, or applesauce fit this approach.

Low glycemic index foods have no proven advantage before a race. In most studies, according to the position stand from ACSM, the Academy of Nutrition and Dietetics, and Dietitians of Canada, neither the glycemic index nor the glycemic load changed endurance performance when carbs and energy were matched.

The last hour: sugar and coffee

You often hear that you should avoid sugar right before exercise because of low blood sugar. Jeukendrup and Killer consider this advice unfounded: eating carbs within the hour before exercise does not hurt performance. Some athletes still feel symptoms similar to low blood sugar, even when their blood sugar isn't actually low. If that's you, note it and adjust during training.

On caffeine, the ISSN says aerobic endurance benefits most consistently, with large differences between individuals.

If your stomach is sensitive

The 2019 consensus reasons by digestive risk. The more sensitive your gut, the more you cut fat, fiber, and protein from the pre-race meal. For the marathon, it prefers a low residue diet. For ultras, it removes foods that have already caused you problems.

Two popular approaches have been studied in athletes. A short gluten-free diet did not improve performance, digestive symptoms, or well-being in non-celiac endurance athletes. A low FODMAP diet (fermentable sugars) improved everyday digestive symptoms in 82% of runners in a small preliminary study, but not the symptoms they felt during exercise.

A joint position stand from sports dietitians (Sports Dietitians Australia and the Ultra Sports Science Foundation, 2025) ranks FODMAP manipulation and gut training among the strategies most often showing favorable results. A 2025 systematic review concludes that the causes are many and that prevention should be individualized. If digestive problems keep coming back, talk to a doctor or a sports dietitian.

What you can do before your next race

The g/kg benchmarks come from the consensus statements. The meal examples are not based on any scientific source; they're illustrations only.

Take a 9:00 a.m. start, 70 kg, with a target of 2 g/kg: 140 g of carbs, eaten around 6:30 a.m. One example meal: white bread with jam, a ripe banana, and applesauce. Add it up with the labels.

• ✓Calculate my range: my weight times 1 to 4 g
• ✓Choose the meal time based on the start time
• ✓Test it before a long run, at the same time as the race
• ✓Note how I feel: stomach, energy, hunger
• ✓On race morning, eat no unfamiliar food

For the pre-marathon carb load, don't try it for the first time on race day. Build up to it gradually before a long run. A 2026 study of only 11 trained people noted increased feelings of fullness with a high carb intake. If that happens to you, stick with what your stomach tolerates.

The long run is the right time for these tests. Log your meal separately, in a notebook or your phone's notes: ELYO does not record what you eat. It does read your workout from your watch and analyzes your pace and heart rate, so you can see whether they held up. If your pace drops after 1 hour on days when you ate less than 2 g/kg, that's a clue.

Written with the help of AI.