Our bodies use two main fuel sources: carbohydrates and fats. Fat is the main fuel source for low to moderate intensity activity while carbohydrates are the main fuel source for moderate to high intensity activity. Carbohydrates should make up the majority of the diet in order to sustain the high demands of training daily. Carbohydrates are stored in the body, primarily in our muscles and liver, as glycogen. A high glycogen concentration in the muscles will allow you to train at your optimal intensity. While a low glycogen concentration will lead to fatiguing quickly, reduced intensity and reduced sports performance.
The optimal carbohydrate intake is completely individualized and depends on the intensity and duration of activity. Consuming carbohydrates are commonly known to improve endurance performance especially in events lasting longer than 45 mins. It is important that sufficient fuel and energy stores are met to avoid depletion and maintain performance levels.
How much Carbohydrate should I consume daily?
Carbohydrate intake should make up roughly 60% of your total daily calories. The baseline carbohydrate intake recommendations are 4-5g of carbohydrates per kilogram of body weight per day, plus an additional 1-1.5g of carbohydrates per kilogram of body weight per hour of exercise.
Endurance training requires a high carbohydrate diet in order to replenish muscle glycogen stores. Generally, endurance athletes should consume 8-12g of carbohydrates per kilogram of body weight per day. For example, a 70kg triathlete would need 560-840g of carbohydrates daily. Low carbohydrate diets can reduce your capacity for high intensity exercise, and you may be at risk of frequent illnesses and injuries.
What, when and how much you eat prior to exercise will affect your performance and endurance. Consuming carbohydrates before exercise can result in improved performance in comparison to exercising fasted (on an empty stomach).
A pre-exercise meal will greatly depend on your schedule and training plan. Ideally, 2-4hrs before training is optimal timing, as it allows for your stomach to settle and so that you’re not too full or too hungry. A pre-exercise snack is often recommended 1-2hrs prior to exercise to top up your glycogen stores.
Carbohydrate loading is a useful strategy especially for endurance and performance athletes participating in events lasting longer than 90mins. It is basically where you up your carbohydrate intake 36-48 hrs prior to the event/competition. For example, carbohydrate loading should be implemented the day before and the morning off race day. This increases muscle glycogen stores above normal levels, and it prevents ‘hitting the wall’, which some athletes may know too well. It decreases your rate of perceived exertion (feels less tough) and prevents fatiguing quickly.
Carbohydrate loading is not about ‘just eating more’. It is about reducing fat, fibre and protein intakes with an emphasis on consuming simple carbohydrate-based foods. Good carbohydrate sources include pasta, rice, potatoes, white bread and plain bagels.
Stay tuned to part 2 of this Carbohydrate Series as we explain in detail race day nutrition, intra performance nutrition and common carbohydrate sources for endurance athletes.
For assistance with managing your sports nutrition or to see if the coaching programme is right for you, you can make an enquiry here.
Written by Aiveen Connolly – M.Sc. SERn performance nutritionist and coach @ Evan Lynch Nutrition