With Boston on April 20 and London on April 26, tens of thousands of runners are entering the final weeks of marathon preparation. While training is largely done by this point, nutrition strategy remains one of the most controllable — and most frequently mishandled — factors in marathon performance. Getting race day fuelling right can mean the difference between a personal best and a painful bonk in the final miles.
Carbohydrate loading should begin 48-72 hours before race day, aiming for 8-12 grams of carbohydrate per kilogram of body weight daily. This does not mean eating more food overall — it means shifting the proportion of your diet toward carbohydrate-rich foods while reducing fibre and fat to minimise gastrointestinal risk. White rice, pasta, bread, and sports drinks become your best friends. The pre-race dinner should be familiar, moderate in size, and consumed at least 12 hours before the start.
Race morning breakfast should be eaten 2-3 hours before the gun and consist of 1-3 grams of carbohydrate per kilogram of body weight — typically toast with jam, a bagel with honey, or porridge with banana. Avoid anything high in fat, fibre, or protein, and stick rigidly to foods you have tested in training. The most common race day nutrition mistake is trying something new on the morning of the race.
During the race, current evidence supports consuming 60-90 grams of carbohydrate per hour from a mix of glucose and fructose sources. Gels are the most practical delivery method, but must be taken with water, not sports drink, to avoid gastrointestinal overload. Start fuelling at mile 4-5 rather than waiting until you feel depleted — by the time you feel the need for fuel, you are already behind on energy. Practice your exact fuelling plan in at least two long runs before race day, using the same products you plan to race with.