Whether you are an advanced, competitive runner or someone who has signed up for the marathon and never run further than 3 miles, the success of your training will depend on how well you fuel your body. Running is an extremely rewarding form of exercise for the body and mind and if you are looking to push yourself and improve body composition it is certainly a great choice!
It can be difficult to gain all the requirements you need through diet, but with a better knowledge of what to eat and when, it can become much easier.
The first issue with training of this magnitude is correctly estimating your energy demands. Most people tend to underestimate the calories that a workout of this nature requires. When you think of the extra energy you will require for mechanical movement, you probably haven’t even considered that the impact of running on lower limbs and recovery from each training session will also require more energy. Your daily intake should be divided as follows; ~60% carbohydrates, 20% lean protein and 20% healthy fats.
We have all hit that ‘wall’ when running, cycling or performing endurance sports due to the depletion of glycogen. Glycogen stores usually range from 100-120mmol/kg of bodyweight, but if these stores diminish, your body begins to mobilise its fat stores for energy. Despite fats higher energy content per gram, it is not broken down as quickly or efficiently meaning you hit a low spot during exercise until the energy can be utilised. In order to increase the time until onset, or reduce the duration of the ‘low’ an athlete should stock up on starchy polysaccharides 2-3 days prior to the event...this is known as Carb - Loading!
Starchy polysaccharides are the main fuel for any activity above and beyond 65% of maximum exertion, therefore an athlete should stock up on starchy polysaccharides 2-3 days prior to the event. During the loading phase, an ideal diet would consist of approx 80-90% carbs, aiming for approx 5-10 grams of carbs per kg bodyweight (Minehan, 2004).
The best sources of starchy polysaccharides (complex carbs) include porridge oats, wholegrain pasta (the wholegrain slows the rate of digestion), potato, sweet potato, quinoa, legumes, peas, lentils and chick peas. Alongside this, starchy carbs also deliver some key nutrients involved in energy delivery, muscle repair and general healthfulness including fibre, calcium, iron and B vitamins.
The focus on carbohydrates for endurance athletes tends to make them neglect their protein and fat requirements. Low dietary protein will increase muscle recovery time and have a detrimental impact on training. It is also more likely that you will suffer from fatigue and anaemia thus undoing all your hard work in training. 1.4-1.7g per kg of body weight is recommended for endurance athletes. I would recommend that you stay at the upper end of this if you are training for a marathon. The use of protein shakes, particularly post-workout, is an extremely good idea when you are training at a high intensity day after day. Although we would usually associate protein supplementation with strength and power athletes, it is also highly important to an endurance athlete.
It is vital that you keep fluid and electrolyte levels as optimum as possible before, during and after training sessions. Do not include caffeinated beverages in your fluid count and try to avoid them when you are not training. They act as a diuretic and will cause you to become dehydrated if you do not use them effectively. The intake of water is vital to the chemical reactions that occur in the body to utilise energy, aid muscle repair and prevent damage to cardiovascular, skeletal and digestive systems. Opt for an isotonic sports drink when training exceeds 90 minutes to help replenish electrolytes and fluid lost through sweat.
Hard training creates free radicals in the body that can lead to serious degenerative diseases. Boost your immune system, and battle those free radicals with foods high in antioxidants. Eat lots of fruit and vegetables, and choose the most colourful ones you can find. Blueberries, oranges, strawberries, red cherries, kiwis, apples, broccoli and carrots all contain high levels of powerful antioxidants that are easily assimilated.
By consuming a high nutrient diet, you will ensure that your body receives the vitamins and minerals it needs to function optimally despite the high stresses placed upon it during training. Eating healthy fats will help you to process vitamins A, D, E and K.
Specific foods which are full of vitamins/minerals/anti-oxidants:
Lean Red Meat – The amino acids will help aid muscle damage and the zinc will ward of infection. The iron in red meat is more easily absorbed by the body than from alternative sources and will help guard against anaemia.
Vegetables – A great source of vitamins and carbohydrates! Load up on carrots as the carotenoids help boost immunity and protect cells from free radical damage.
Eggs – An excellent source of protein and vitamin K.
Potato – Though many people avoid these when eating a healthy diet, they are a great source of fibre, vitamin C and of course, carbohydrate. They are easy to digest which makes them great for pre or post-training meals.
Quinoa – This relatively unknown superfood is a great alternative to pasta or rice. It is high in protein and is an excellent source of magnesium, iron and dietary fibre.
Walnuts - a great snack to include in your diet as they contain high levels of omega 3. Omega 3 is a fatty acid which the body cannot make itself but is necessary to the upkeep of your body. It plays a role in inflammation reduction and lowers LDL (bad) cholesterol.
Salt Tablets – These will aid fluid retention helping you to avoid inconvenient trips to the toilet during mammoth training sessions and ensure your sodium and potassium levels remain normal.
Meeting Energy Demands
One of the main consequences of training is perspiration (sweating) and energy store depletion. Therefore achieving the ideal ratio between electrolyte and water is integral, and is achieved through the replenishment of body water, electrolyte, and moderate to high glycaemic index carbohydrate. During intense physical activity, you can quite feasibly lose 1 litre of fluid an hour, and depending on exercise intensity and ambient air temperature, this value can increase to more than 3 litres!
The average isotonic beverage delivers fluid, salt, glucose, fructose, maltadextrin and minerals, meaning consumption of these drinks supply a surge of semi-sustainable carbs lasting approx 30mins, plus a faster fluid and electrolyte absorption rate via osmosis (salt is rapidly absorbed drawing fluid into the circulation) to sustain muscle mineral balance and hydration (Metzger, 2008).
Isotonic powdered formulas and pre-made bottled beverages deliver fluid, electrolyte and carbs all in one! They contain expertly moderated quantities of sodium, which is integral to maintaining electrolyte balance and therefore training capacity. Depletion of any mineral impacts on muscle contractile tissue and energy delivery! Sodium is also vital to rehydration, through consuming Sodium your body absorbs more water via a process known as osmosis (movement of water from an area of low solute i.e. sodium concentration, to an area of high). This osmotic shift speeds up the absorption rate of fluid, promoting thirst and further encouraging hydration!
Energy gels are a great alternative to isotonic drinks. The bloating and ‘stitch’ that can sometimes accompany liquid energy replenishment during training can be avoided if a more concentrated source of glucose and/or maltodextrin is consumed. The average energy gel comes in the form of a small and convenient 35g sachet. They are easily consumed and readily absorbed, providing a rapid delivery of carbohydrate to the muscles. The inconvenience and digestive difficulties that can result from consuming a carbohydrate bar mid- exercise, make energy and electrolyte gels an ideal training accompaniment.
Williams C, Brewer J & Walker M, The Effect of a High Carbohydrate Diet on Running Performance During a 30km Treadmill Time Trial, European Journal of Applied Physiology, 1992, 65: 18-24.
Bussau VA, Fairchild TJ, Rao A, Steele P & Fournier PA, Carbohydrate Loading in Human Muscle: An Improved Day 1 Protocol, Journal of Applied Physiology, 2002, 87: 290-295.
Metzger J, Carbohydrate Super‐compensation: Fact or Fiction? Understanding the Truth Behind Carb‐Loading, Science In Sport, 2008.
Minehan M, Department of Sports Nutrition, Australian Institute of Sport, Carbohydrate Loading, 2004.