The role of sugar and carbohydrates in physical performance and exercise

: 02 December 2020

As humans, we’ve been interested in which foods help us reach the highest capacities for physical performance since the dawn of time.

From foods and drinks used in rituals to attain a higher knowledge through to foods that have a physical effect on our bodies like caffeine and chilli, humans have always been fascinated with foods that can assist us in pushing the boundaries of what our bodies can do.

Many different food types have a significant impact on our exercise performance and for the purposes of this article, we will be focusing on carbohydrate-rich foods as a fuel source and their influence on physical performance and exercise.

Carbohydrates and diet

The Australian and New Zealand guidelines suggest that between 45% and 60% of our overall energy intake should be from carbohydrates, 20% to 35% from fats and 15% to 25% from protein. If however, you’re an athlete or perform regular strenuous activities, it’s likely you will need a slightly higher carbohydrate intake than the average person.

The types of carbohydrates you ingest will have dramatically different results on energy production, total nutritional value and the effect on blood glucose. Different types of physical performance will create different demands on the body and the way it burns fuel, so understanding how the body burns and uses an energy source like carbohydrates, and tailoring your diet to suit, can help performance.

Importance of carbohydrates for exercise

Key energy source	Carbohydrates provide the body with its first option for energy and are a key fuel for the brain and central nervous system. During any type of activity, muscles use glucose from carbohydrate for fuel.
Easily digestible	Carbohydrate foods are an easy option prior to exercise. They are generally well tolerated and preferred by athletes, and are easily digested compared to fat or protein foods.
Versatile	Carbohydrates can support exercise over a range of intensities due to its use by both anaerobic and oxidative pathways. For short, high-intensity exercise, the main source of energy is glycogen (glucose) stores in muscle and the liver. For longer duration exercise, carbohydrate utilisation will vary depending on intensity, type of training and overall diet.
Improved performance	Performance of prolonged, sustained or intermittent high-intensity exercise is enhanced by high carbohydrate availability and matching glycogen stores and blood glucose to the fuel demands of exercise. In contrast, depletion of these stores is associated with fatigue, reduced work rates, impaired skill and concentration, and increased perception of effort.
Easily manipulated	The body’s carbohydrate stores are relatively limited and can be manipulated on a daily basis, or even during a single session of exercise, though dietary intake to match the requirements of exercise.

Due to the above factors, the low availability of carbohydrate stores can play a major limiting factor for exercise performance. A key strategy in promoting optimal performance in competitive events or training is matching an athlete’s carbohydrate stores with the fuel demands of the session, with a focus on dietary carbohydrate pre, during and post exercise. For more information, take a look at Can athletes eat sugar?

Carbohydrates and endurance capacity

Many studies have shown there is a link between diet and exercise capacity, in particular endurance capacity. Many athletes find that endurance capacity increases dramatically after a period eating a high carbohydrate diet, whereas the opposite was true for those eating a high fat and high protein diet (endurance capacity was greatly reduced).

If you are competing in endurance events (typically an event that involves over 90 minutes of continuous high-intensity exercise that uses the same muscle group) the chances you will burn through the body's normal fuel stores is very high.

By consuming a high carbohydrate diet in the days before an event, this will help your body load glycogen stores in your muscles which can help athletes avoid (for a time) ‘hitting the wall’, which is a common symptom muscle-glycogen fatigue.

Not all carbohydrates are built the same

The simplest carbohydrates we consume in western society are monosaccharides, or simple sugars. Monosaccharides are the building blocks of all sugars and carbohydrate. They can be found in foods like honey, dried fruits, yogurts, Power Bars and meal supplements, sports drinks, and of course cakes, syrups, lollies and sugary drinks.

While all these foods contain carbohydrates, the difference is in the overall nutrient content of the food. Fresh fruit, light-style muesli and yogurt provide valuable vitamins, minerals, proteins and fibre for a moderate kilojoule intake, whereas more ‘refined’ foods like cakes and soft drinks have gone through multiple processes which may remove some of the nutritional benefits and dilute their nutrient to energy ratio.

With this in mind, if you’re looking into carbohydrate loading for endurance events, sports dietitians recommend you don’t fuel up with chocolates, rich desserts and fatty pasta dishes.

Foods with complex carbohydrates like oats with milk and honey, wholemeal bread rolls with meat and salads, fresh fruit, etc are better options for carbohydrate intake. On the day before racing, many athletes like to focus their diet on low-fibre (low-residue) eating so they can race ‘light’ and avoid stomach discomfort.

On race day, compact carbohydrate-rich foods like sports gels, sports bars and sports drinks can give athletes the energy boost they need without leading to gastrointestinal fullness.

Carbohydrates and recovery

As with performance, carbohydrates play an important role in recovery from high-intensity activity. After hard training or events, it’s imperative to replenish muscle fuel stores, and carbohydrates are an important part of this process. As different sports use different muscle groups for a range of different timeframes, exact amounts of carbohydrates to promote glycogen storage will vary.

The recommended amount of carbohydrates for full recovery is 7-12grams per kg of body mass. As mentioned previously, not all carbohydrates are the same, so high-carbohydrate foods with a moderate to high Glycemic Index are recommended, thus enabling athletes to incorporate a range of different foods into their recovery meal plans.

Looking for further information about sports performance and carbohydrates? Take a look at Are low carb high-fat diets for sports performance all hype?

REFERENCES

Mann J and Truswell AS (2002). Essentials of Human Nutrition. Oxford:Oxford University Press.
Academy of Nutrition and Dietetics, American College of Sports Medicine, and Dietitians of Canada (2016). Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet, 116: 501-528.
Bourke L & Cox G (2010). The Complete Guide for Food for Sports Performance: Peak Nutrition For Your Sport. Australia: Allen & Unwin.