Marathon nutrition: what should you eat during training?

For marathon runners, carbohydrates are the most practical performance lever. They help replenish glycogen, the fuel heavily used during quality sessions, long runs, and the marathon itself. As training load rises, carbohydrate intake generally needs to rise too. During harder weeks, many runners do well with roughly 6 to 10 g per kilogram of body weight per day, adjusted for volume, intensity, and appetite.

Protein serves a different purpose. It supports tissue repair, recovery, and maintenance of lean mass while fatigue accumulates. A common endurance target is around 1.2 to 2.0 g per kilogram per day, ideally spread over several meals. Fats should not be cut aggressively either. They contribute to energy intake, hormones, and satiety. The goal is not to turn nutrition into a macro obsession, but to make sure each macronutrient does its job.

In a normal training week, the main goal is to place energy around key sessions. Workout days and long-run days usually justify more carbohydrates before and after the session: rice, pasta, potatoes, bread, oats, fruit, or simple snacks. Very easy days do not need the same intake. That basic variation helps runners avoid under-fueling hard work and overcompensating randomly later.

Race week follows a different logic. The job is no longer to create adaptation, but to arrive with available energy and a calm gut. That usually means familiar foods, simpler meals, more carbohydrate density, and relatively less fat, spice, or fiber if your stomach is sensitive. The best pre-race meal is usually the one you know you can repeat without stress.

If your long run is in the morning, race-day fueling actually starts weeks earlier. A common guideline is to eat about 1 to 4 g of carbohydrate per kilogram of body weight in the 1 to 4 hours before exercise, adjusting the amount to your available time and gut tolerance. The earlier you eat, the more you can include. The closer you are to the start, the simpler the meal should be.

The most common mistake is copying another runner's breakfast and discovering too late that it causes heaviness or stomach discomfort. Long runs are where you rehearse your future race breakfast, drink strategy, and in-run fueling. If you run very early and cannot manage a full meal, a lighter option such as a banana, applesauce, half a bagel, or a sports drink can be enough before topping up during the session.

Hydration is not about chugging water right before the session. A better approach is to arrive already well hydrated from the previous day, then top up based on weather, duration, and thirst. Watching urine color, dry-mouth sensation, and body-weight changes after long runs can already give useful clues. On short easy runs, water is often enough. On longer or hotter sessions, sodium-containing drinks can make more sense.

Electrolytes matter most for runners who sweat heavily, leave salt marks on clothing, or train beyond 90 minutes. The goal is not to overload sodium, but to better match losses and improve fluid retention. The marathon should be rehearsed in training, so test your drink volumes, timing, and electrolyte strategy on long runs rather than leaving those decisions for race morning.

The final week should not turn into a giant pasta challenge. The logic is simpler than that: training tapers down, fatigue drops, and carbohydrate intake rises to top up energy stores before a long event. For runners who tolerate it well, carbohydrate loading can reach roughly 10 to 12 g per kilogram of body weight per day during the final 36 to 48 hours before the marathon.

In the last two days, many runners benefit from reducing bulky fiber sources, large raw salads, heavy sauces, and any experimental food. The night-before dinner should feel reassuring, not heroic. On race morning, the answer is the same as during your best long-run rehearsals: a familiar carbohydrate-rich breakfast eaten early enough to digest comfortably, followed by a calm hydration routine.

Good marathon nutrition is not a rigid diet or a list of miracle foods. It is a practical system that follows your training load, protects long-run quality, and reduces guesswork during race week. When carbohydrates are sufficient, protein is regular, hydration is rehearsed, and your breakfast is already tested, a lot of invisible preparation stress disappears.

Nutrition does not replace a strong training plan, but it determines how much of that plan you can actually absorb. When both work together, recovery improves, consistency gets easier, and race week feels far more controlled.