The importance of carbohydrates
Carbohydrates are no doubt the energy powerhouses for fitness. High carbohydrate foods (such as whole grains, cereals, fruits and vegetables), all supply energy to your working muscles during exercise. They also offer a variety of important nutrients like vitamins C and A, and antioxidants, crucial for maintaining healthy cells in the body.
No matter what type of exercise you do, your body will always use some glucose for energy. Glucose is formed from the breakdown of carbohydrates (sugars and starches) in your diet and is stored as glycogen in the muscles and liver. However, the body can store a limited amount of glycogen, and to keep it topped up you need to refuel with carbohydrates within two hours of exercise as well as eating a carbohydrate-rich diet overall. How much carbohydrate you need really depends on the amount of training you do – the more glucose you use the more you need to eat to replenish your stores.
Your carbohydrate needs
The amount of carbohydrate you need depends on the amount of exercise you do. Research has shown that a diet high in carbohydrate, obtained either from simple sugars or complex carbohydrate, is equally effective in improving exercise performance. If you’re physically active, the optimal diet is one that contains 60-70% energy from carbohydrates. However, it’s difficult enough to guesstimate the proportion of carbohydrate containing foods in one meal, let alone drinks and food for the rest of the day!
Which carbohydrate?
Most carbohydrate foods such as pasta or sugars are eventually broken down into glucose, so one type is not intrinsically better than the other. Having said that, what is important is how quickly the carbohydrate is converted to glucose - and that’s where the glycaemic index (GI) is useful.
The GI of a food is a measure of that food’s effect on blood glucose levels. It is calculated by comparing the rise in blood glucose after eating a food containing 50g of carbohydrate with the blood glucose rise after eating 50g of a reference food (usually glucose). The faster the rise in blood glucose, the higher the GI. The table below gives the GI category of some everyday foods. Unfortunately, there is no easy way to tell what the GI of a food is. Some sugars have a high GI (glucose) and others a low GI (fructose). Some complex carbohydrates have a low GI (pasta) whereas others have a higher GI (rice).
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