More Carbs Can Better Support Marathon Training

Marathon preparation raises carbohydrate needs because the body relies on carbs as its main fuel. When too little is available, it may use muscle for energy instead. Getting enough carbohydrate before and during a marathon can also support performance in the later miles and reduce the chance of bonking. Possible signs of insufficient carbs or overall calories include persistent tiredness, irritability, a higher exercise heart rate, trouble maintaining a planned pace, or an easy pace suddenly feeling hard.

Brian St. Pierre, RD, CSCS, recommends 5 to 7 daily grams of carbohydrate for each kilogram of bodyweight during maintenance or base-building. Near peak marathon training, that range rises to 6 to 10 grams. Lindsey M. De Caro suggests making complex carbohydrates—such as fruit, starchy vegetables, and whole grains—roughly 50 percent of the plate. As mileage increases, simple-carb additions can include crackers or juice. She favors eating a carbohydrate source at every meal, with extra carb-rich snacks on demanding training days.

Protein remains important, particularly after difficult sessions. For marathon runners, St. Pierre gives a daily range of 1.4 to 1.8 grams for each kilogram of bodyweight, while De Caro suggests about one-quarter of a plate. More carbohydrates do not always require more total food: protein-heavy choices can be exchanged for carb-rich ones, since each nutrient supplies four calories per gram. Examples include spreading less chicken across two wraps, replacing egg whites with blueberries alongside oats, or adding wild rice, quinoa, or sourdough bread. Quinoa, beans, legumes, and Ezekiel bread can provide both nutrients, though excess fiber may create fullness or digestive difficulty. Easily digested choices such as white rice can therefore have a place. Carbohydrates consumed during runs are another opportunity to maintain fuel, including on outings beyond the weekly long run.