Is carbohydrate friend or foe to the endurance athlete?
As an endurance athlete, do you need to eat carbohydrate for training and racing? The answer is, it depends.
Over recent years, many books have been written about the low carb high fat (LCHF) endurance athlete. They are full of case studies reporting athletes who do endurance events on less than 50g of carbohydrate a day. The view is that you can cut carbohydrate out of your day to day eating and increase your fat intake, your body will then use fat instead of carbohydrate as its primary energy source. This is seen as a positive as we can only hold around a day’s supply of energy as glycogen in our muscles yet even at low body fat percentage we have enough energy for nearly a month !
My personal view is that it’s not quite as straight forward as this and to understand it better we need to look at how our body is designed to work.
There are 3 different pathways that the body can choose to make energy we need to train and race as endurance athletes:
The creatine phosphate system – I like to think of this as ‘first gear’ this is used for high intensity, short duration exercises where energy is required quickly. Examples of activities which use this might be a 100m sprint or heavy weight lifting. This is an anaerobic (without oxygen) energy pathway and it doesn’t use carbohydrate or fat stores.
The lactate system – this system is a bit like ‘second gear’, it is the system you probably associate with that burning sensation in your muscles during high intensity exercise. It can supply energy for higher intensity exercise for approximately 60-180 seconds. This is also an anaerobic pathway and it will be at around 75-95% of your maximum heart rate. Your body uses carbohydrate in the form of glucose to fuel this pathway and it is the by-product lactic acid which causes the burning sensations in your muscles.
The Aerobic (oxygen) system – This is the energy system which produces energy from the complete breakdown of carbohydrate and fat in the presence of oxygen. It’s like ‘third and fourth gear’ .This energy system is dominant during low to moderate intensity activities up to 75% of maximum heart rate. The by-products of the aerobic system are carbon dioxide which is breathed out and water which is either used by cells in the body or lost through sweat.
In a healthy, metabolically flexible body, there is considerable overlap between these three energy systems and all 3 of them can provide the body with energy it needs simultaneously. The amount of energy a system contributes, will depend on the intensity of the training and racing.
Unfortunately, due to the high percentage of refined carbohydrates which feature in the day to day eating of so many people, these 3 systems are not able to operate so effectively and efficiently. Instead of using fat at low intensity, their body becomes very reliant on carbohydrate . Consequently, during endurance events, instead of using fat for most the race, they will use carbohydrate. This will run down their liver and muscle stores of glucose (glycogen) more quickly and mean a higher risk of bonking.
The best way to re-set your metabolism and get it back to using the 3 energy systems efficiently and effectively is to remove all refined carbohydrate from your diet and decrease your daily carbohydrate intake to less than 50g per day. This is best done outside of race season. It will take 4-12 weeks for your body to adjust and go back to using fat as its fuel for low intensity training and racing. Once you have achieved this, you can then increase your carbohydrate slightly to find your ‘sweet spot’ for higher intensity training. When you then use carbohydrate during racing, your body will use it to produce energy when it needs it at higher intensity rather than all the time. This means that you have a better chance of finishing your races without running out of energy.
In summary carbohydrate can be both friend and enemy to an endurance athlete. To use it as a friend, you want to ensure that your body is metabolically flexible burning mainly fat at low intensity and taking full advantage of carbohydrate as ‘rocket fuel’ at higher intensities. By getting your body to operate in this way, you decrease your risk of heart disease and diabetes. You will also be able to shift that stubborn body fat.
Being leaner and lighter with full energy stores will mean you get faster too. If you need help in making sure your body is metabolically flexible then get in touch firstname.lastname@example.org I’d love to help.