Carbohydrate FAQs

Carbohydrates provide the energy needed for physical activity; essentially fuel for exercise is the food we eat. The body converts carbs into glucose which is carried to the cells and used as glycogen for energy. If you don't have enough glycogen this can cause fatigue, reducing your performance and immune system. It is therefore important to plan your carb intake carefully, ensuring that you have enough energy, particularly for long periods of exercise. 

When exercising for periods of over an hour, carbs are very important as a more rich source of energy than fat and protein stores. When eating carbs before and during exercise, your performance ability will increase mainly due to having increased glycogen available as energy. Sports drinks can be an easy option, giving you both energy and hydration before, during and after your workout. Endurance capacity can even double when compared to a normal diet, and will even reduce if you are eating a high fat or protein diet. If you are exercising over a long period of time at a relatively high intensity, a high carb diet will be best to provide you with enough energy to last for a long time without fatigue or exhaustion. 

A number of factors affect how much carbs we need, including the individual, exercise intensity and duration, but generally for an athlete, 60-70 per cent of energy should be from carbohydrates. High intensity exercise of around 1-3 hours requires 6-10g per kg of body mass, compared to low intensity exercise needing only 3-5g per kg of body mass.  Carb intake is dependent on the type, intensity and duration of exercise, increasing the amount of carbs eaten when increasing the intensity of the workout. Trainers and planning are very useful to help you calculate how much carbohydrate you will need for your exercise, as exhaustion of carbs will cause the body to use its fat and protein stores as fuel, potentially burning muscles as fuel instead of food. 

Some people think that to build muscle quickly, carbs must be sacrificed to burn off fat as fuel and packing on the protein instead to help grow muscles. This is true when athletes try and lean up for a short period of time, but throughout most of the year, when trying to pack muscle on and expand growth, a moderate to high carb diet is the best technique. Higher energy levels, increased muscle support, increased recovery rate and the prevention of muscle breakdown are all guaranteed when you eat carbs. Contrary to popular belief carbs can actually assist your muscle growth making them stronger, and should definitely be included in your diet. 

Your performance firstly decreases when you skip or use up all your carbs, muscle movements and motivation both become more difficult, which can then affect performance. When carb stores have been used up, the body will then use protein as it’s energy source, which subsequently will affect it’s ability to gain and support muscles. Burning protein as energy can cause further problems as when your body tries to clean out the byproducts of protein, your kidneys have to work harder, causing stress which could result in damaging them. Carbs also help fueling the brain and central nervous system, and when you have run out of carbs, this can affect their functioning and can in serious cases lead to further problems. 

Any unused energy is stored in muscles and liver for energy, once reached its max of 300-400 grams, it is then converted and stored as fat in tissues. Much debate has surrounded whether cutting carbs will result in weight loss and fat reduction, however low carb stores can result in adverse effects particularly on exercise, such as fatigue and the need for longer recovery times after exercise. Instead many diets, nutritionists and doctors recommend the exclusion of only certain carbohydrates. Whole-wheat carbohydrates, beans, oats and so on provide a healthier option as they take longer to be absorbed into the blood, low GI, which are a better source of energy for those wanting to cut fat without damaging the body and exercise regimes. 

Ingestion of carbs before exercise is important, mainly for the purpose of topping up energy stores in muscles and the liver, and so fatigue delay and performance can be improved by ensuring these stores are high when first beginning exercise. Eating carbs will therefore be beneficial both during and after exercise, helping you feel the benefits of your sport and exercise. For high endurance sports it is best to maximise glycogen stores in the days leading to an event by carbo-loading the few days prior to an event. 

Topping up glycogen or carb stores after exercise is very important for recovery, along with protein for the repair and growth of your muscles. It is best to eat carbs relatively soon after exercise to ensure the muscles have plenty of energy available. How quickly you recover following exercise is dependent on how well your muscles have been replenished with energy, as reduced stores can result in fatigue and your ability to train again will be decreased. The optimum time for recovery is to consume some carbs (plus protein) in the first two hours after your exercise, both solids and liquids can be used to replenish stores and so a variety of foods and drinks are available to you to help restore fuel levels. 

When you partake in moderate cardio exercises your body is most efficient at using fat stores as fuel, as a decreased intensity doesn’t requires an immediate source of fuel which would be satisfied by burning carbs. When doing intense or long periods of exercise however, extended workouts such as hard weight training or cardio workouts, your body will use carbs as its first source of fuel and it is therefore important that you consume some before exercise. Harder workouts require a more immediate and intense supply of energy, this is easily accessed by our carb stores due to their easily broken down nature.

Lots of different foods and drinks contain carbohydrates, though they are classified by how quickly the body can break them down and release the energy. Low GI carbs are preferred as they provide a longer and more sustainable source of energy. Different fruits such as bananas and berries can be a healthier option as a snack or pre-workout bite, but also rich in energy and nutrients. Whole grain and wheat products such as pastas, bread and rice are a good source of healthy carbs for meals as they release energy slowly, ideal for before and after exercise.