How do you fuel your training? Sports drinks, sports bars, sports gels, jellybeans and flat cola all help us to train fast during exercise. Then we keep topped up with rice, pasta, bread, potato, bananas, cakes and cereals at home and during the day and so provide our body with all the fuel necessary to do the sport we love. But how healthy is this in the long run? How effective is a high carbohydrate diet for endurance athletes? And are there any detrimental effects?
Where do we store our energy? A little bit about body fuel…
Our body uses various fuels including fat, protein and carbohydrate. In addition to this, energy is also stored in alcohol although this is not a useful energy source and cannot be considered fuel for sport. In energy terms fat has the highest energy density of 9kcal/g, compared to 7kcal/g for alcohol, and 4kcal/g for both carbohydrate and protein. So to get the same amount of energy you have to eat more than double the amount of carbohydrate as you do fat.
Where we store our fuel depends on the timing and type of food we eat. In terms of a fully fuelled adult body, we store enough carbohydrate energy in muscle cells and liver (stored as glycogen) to fuel about 2 hours of continual aerobic exercise such as cycling. In contrast to this we store enough energy as fat to fuel 40 times this. So why do most endurance athletes focus on a high carbohydrate and very low fat diet?
Accessing the stored energy is crucial for it to be useful in sport, and this is where the difference lies between stored glycogen and fat. Glycogen is highly accessible and quickly used in sport, and even more so as the intensity increased. The blood glucose is replenished by the muscle glycogen as it depletes and is easily used to fuel sport. Fat on the other hand is far less accessible and is a much slower source of energy. It certainly is our main fuel source in sedentary life, but as sport intensity increases the percentage of energy used from fat decreases as the glycogen use increases.
Since we only have a couple of hours worth of glycogen storage in our muscles, we do re-fuel with sugary sports drinks, which are rapidly absorbed into the blood stream and either prevent the glycogen depletion or replenish lost energy, resulting in better and prolonged sports performance.
With this in mind the traditional endurance diet is therefore considered optimal with approximately 70% of energy from carbohydrates, and the rest from protein and fat.
Periodise your food like your training
Is a blanket nutrition rule applicable to everybody though? Imagine if you only exercised the same type and intensity of exercise every day. You would soon stop seeing results and you’d feel monotony and boredom quite quickly. So why would we not adapt our eating to meet the demands of the activity we do.
Anti-nutrients in the athlete’s diet
If a food type supplies energy to the body, but little in the way of nutrients it is termed an anti-nutrient. Examples include grains and sugar, which account for the majority of the average endurance athlete’s diet. Pasta, bread, potato, cereal, sports drink, and sports bars all supply what can be described as empty calories. They provide energy but little nutritional benefit, and may even deplete the body of vitamins and minerals. An example would be the massive reliance on wheat for energy that results in an acidic environment in the body. To counteract this the body will call upon it’s alkaline stores (calcium from bones) to neutralize the acid, but wheat does not provide the materials to replenish these stores.
Meat and ten veg please
So what can be done to ensure our bodies are getting the nutrients needed and the required fuel? We need to consider our nutrition not just as fuel but as nutrients too. The government’s five a day may well be a start but for optimal nutrition, especially for athletes, we really should be looking closer to 10 servings of vegetables per day.
Green leafy vegetables have an alkaline effect on the body, and the more colours and dark vegetables you get on your plate the more antioxidants, minerals, vitamins and fibre you will be consuming. Getting your carbohydrates from nutrient-dense fibrous vegetables rather than nutrient-sparse grains, potato and sugar will ensure energy is topped up during your sedentary day.
In addition to fruit and vegetables, grass-fed organic meat, game meats and line-caught fish such as mackerel, salmon and trout will supply amino acids, minerals and essential fatty acids including omega 3 which are essential to health.
Top Tips to get the most from your carbs
Keep the high-carb refined foods in your diet when they are needed for sport, but consume fibrous carbohydrate sources during your sedentary day.