The term carbohydrate is synonymous with sports nutrition. The immediate impact of carbohydrate intake (or its absence) on daily training and competition performance has been widely researched and documented. Recent media attention directed at public health issues, however, has suggested low carbohydrate diets are beneficial for weight loss and other health benefits. In addition, different approaches to fuelling sports performance become an item of discussion among scientists or the locker room from time to time. It is no wonder many recreational and elite athletes remain unsure of the amount of carbohydrate they need to support their training and competition to optimise performance while achieving a weight and body composition that is appropriate for their sport.

Why is carbohydrate important?                   

Carbohydrate is a key fuel source for exercise, especially during prolonged continuous or high-intensity exercise. The body stores carbohydrate as glycogen in the muscles and liver, however its storage capacity is limited. When these carbohydrate stores are inadequate to meet the fuel needs of an athlete’s training program, the results include fatigue (staleness), reduced ability to train hard, impaired competition performance, and a reduction in immune system function. For these reasons, active people are encouraged to plan carbohydrate intake around key training sessions and over the whole day according to their carbohydrate requirements as an exercise fuel.

How much carbohydrate do athletes need?

Carbohydrate requirements are dependent on the fuel needs of the athlete’s training and competition program, with parameters including the frequency, duration and intensity of the activity. Since activity levels change from day to day, carbohydrate intake should fluctuate to reflect this. On high activity days, carbohydrate intake should be increased to match the increase in activity. This will help to maximise the outcomes from the training sessions and promote recovery between sessions. Alternatively, on low or no training days, carbohydrate intake should be reduced to reflect the decreased training load. .  A clever way to adjust carbohydrate intake from day to day is to schedule carbohydrate-rich food choices at meals or snacks around the important training sessions.  As the sessions increase in their carbohydrate demands, so should the athlete increase their carbohydrate intake before, during or after exercise.  Not only does this strategy help the athlete to keep track of their total carbohydrate needs, but it ensures that the timing of the carbohydrate is best suited to fuel the session. 

The following table provides some general targets for daily carbohydrate intake goals across a range of activity levels. Each athlete should fine-tune their carbohydrate intake with individual consideration of total energy (kilojoule) needs, specific training demands, and feedback from training performance. Additional guidelines outline the specific ways in which carbohydrate intake can be timed to enhance carbohydrate availability for key sessions.

Daily Needs for Fuel and Recovery:

Acute Fuelling Strategies:

Which foods are good sources of carbohydrate?

Many everyday foods and fluids contain carbohydrate, but have different features. For this reason, carbohydrate-containing foods and fluids are often divided into categories for comparison. Previously, carbohydrates were classified as either simple or complex, and more recently, the terms low and high glycemic index (GI) are being used (more on GI below). From a sports nutrition point of view, it is more helpful to classify carbohydrates as nutrient-dense, energy-dense or high-fat.

What about Glycaemic Index?

Glycaemic Index (GI) is a ranking of how quickly carbohydrate foods raise blood glucose levels (BGLs) in the body following ingestion. High GI foods are rapidly digested and absorbed by the body and raise BGLs quickly. Low GI foods, on the other hand, are much slower to be digested and absorbed and result in more gradual rise in blood glucose levels. Refer to the official Glycemic Index website for more information (http://www.glycemicindex.com/).

In sport, it is important to consider immediate requirements and what a whole food or snack can provide (such as protein, vitamins and minerals) rather than  looking at only one component of any food. For example, higher GI foods can be useful immediately after exercise to promote a faster recovery of muscle glycogen stores. Daily requirements, based on physique and performance goals should also be considered when making such food choices.

When is carbohydrate important?

An individual’s carbohydrate requirements before, during and after training or competition depend on a number of factors including:
• type, intensity, duration of exercise
• frequency of exercise or time available for recovery between sessions
• body composition goals
• environmental conditions
• training background
• performance goals for the session.
While the recommendations provided above considers the overall carbohydrate needs over the day, it is also important to consider the timing of carbohydrate around training and competition.
Carbohydrate ingestion before exercise should assist in topping up blood glucose levels as well as glycogen stores in the muscle and liver. This is especially important if the competition or training is undertaken first thing in the morning or if the event is high intensity or will continue beyond 90 mins in duration. Refer to Carbohydrate Loading and Eating Before Exercise fact sheets for further information.
The replacement of carbohydrate during prolonged exercise can benefit sports performance, both through effects on the muscle (reducing/delaying the decline in exercise intensity with time) and the brain/central nervous system (reducing/delaying the decline in concentration and mental skills, as well as reducing/delaying the decline in pacing strategies with time).  Using specific training sessions to practice consuming specific carbohydrate foods is also important if it is intended to be consumed during a competition.
Carbohydrate intake after exercise is essential for optimum recovery of glycogen stores. Often athletic performance is dependent upon the ability to recover from one session and do it all again in the next session. Incomplete or slow restoration of muscle glycogen stores between training sessions can lead to a reduced ability to train and a general feeling of fatigue. In competition, it may also reduce subsequent performances where efforts are repeated within or across days (such as in a tournament, a swim or athletics meet, or a rowing regatta).  Refer to the Recovery Nutrition fact sheet for more detailed information.

In order to ensure your carbohydrate needs are met, and that you are achieving optimum performance, please see a sports dietitian who can tailor a nutrition program to help you achieve your goals.

Food Portions Providing 50 g of Carbohydrate

(Source: Peak Performance: training and nutritional strategies for sport J. Hawley and L. Burke. Sydney: Allen & Unwin, 1998).

Written by AIS Sports Nutrition, last updated October 2011. © Australian Sports Commission.