How to fuel a marathon

Welcome to our brand-new nutrition blog, where Dr James Morton, Senior Sports Nutritionist for Science in Sport (SiS), will be giving advice on nutrition, dispelling fuelling myths and offering his tips every month. If you have a sports nutrition question or area you'd like to see covered in the blog, email editor@runnersworld.co.uk.

James has led and collaborated in over 40 research papers and publications and is also Senior Lecturer in Exercise Metabolism & Nutrition at Liverpool John Moores University (LJMU).

Running a marathon is one of the toughest endurance events that you can undertake. In addition to physical fitness and mental toughness, nutrition is one of the most important factors in predicting your race time. It can be the difference between achieving a personal best or even failing to complete the race.

The build up: the days leading up to the race

Carbohydrates are the major energy source for moderate to high-intensity activity and it is crucial you increase the carb intake in your diet for at least two days prior to the race. A typical carb-loading strategy involves consuming 8-10g of carbs for every kilo of your body mass. For example, a 70kg runner would need 560-700g of carbohydrate each day.  In practice, you could eat extra portions of breads, potatoes, pasta, rice, energy bars and cereals. It can be hard to achieve such high carb intakes from food alone and it is useful to consume drinks containing carbohydrates to further increase your intake. In recent years, dietary nitrates (usually found in root vegetables such as beetroot and spinach etc) have been shown to improve endurance performance by reducing the oxygen cost of exercise and improving the efficiency by which our muscles produce energy. Given that the nitrate content of root vegetables can vary significantly, an appropriate strategy to increase nitrate availability is to consume two nitrate gels five days prior to the event.

Race-day morning: the pre-race meal

Having successfully carb- and nitrate-loaded in the days preceding the event, it is important not to make the mistake of over-eating in your pre-race meal. The purpose of this meal should be to simply top up carb stores without running the risk of feeling bloated before the race. A simple serving of porridge, wholemeal toast, yoghurt and apple juice 2-3 hours prior to the race is likely to be sufficient, though food choices should be tailored to your own taste preferences. Ensure effective hydration prior to the race, too.

During the race: fuelling strategies on the run

Depending on race pace, stored carbohydrates can become depleted after 90 minutes of exercise. Consuming additional carbs during the race (and preventing excessive dehydration) is crucial to achieve your target time. Traditional advice is to consume around 60g of carbs per hour, either in the form of gels, drinks or solids depending on your preference. Carb drinks are beneficial as they provide carbohydrates and help to maintain hydration. However, some runners prefer to consume carbs in the form of gels (so as to avoid feelings of being bloated and for their practicality) and achieve their hydration targets by drinking electrolyte drinks to thirst (usually around 500ml per hour) at regular feeding stations. Practise your race strategy in training and to do what works for you. If it is a particularly hot day, then you may need to consume more than 500ml of fluid per hour and this will likely be led by your thirst. Consuming caffeine gels with around two hours left to complete will also help to give a mental and physical boost during that last hour when you really need it. It can be particularly hard to take on sufficient fluids when you’re running and relying on feed stations, so really make it a priority in your race strategy.

After the race: recovery nutrition

After finishing the race, the goal is to replace energy stores and fluid as well as reducing muscle damage and promoting muscle repair. It’s tempting to forget and just celebrate once you’ve finished, but recovery is incredibly important. Fluid should be consumed at a rate of 1.5 litres per kilo of body mass lost. Carbohydrate should be consumed at 90g per hour for at least three hours and should also be consumed as a mixture of drinks and solids. At least 30g of protein should be consumed within 30 minutes of the race finishing to promote post-exercise muscle recovery. Pre-pack your kit bag with carb-rich foods as part of your recovery strategy: sandwiches, pasta pots, yoghurts and a good old bar of chocolate are all good choices!

Find out more about SiS's range of nutrition products including GO Isotonic gels, GO Nitrate gels, GO Hydro, GO + Caffeine and REGO Rapid Recovery at www.scienceinsport.com.