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Eating to win: activity, diet and weight control
Eating to win: activity, diet and weight control

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5.1 The role of the glycaemic index

The glycaemic index (GI) describes the rate at which carbohydrate foods are digested (broken down into glucose) and enter the bloodstream as glucose. You may already be aware of GI in the context of weight loss diets and healthy eating. The GI also has an important role in maintaining energy levels for physical activity and sports performance. The GI is a ranking of foods from zero to 100, based on the rate at which a carbohydrate food is broken down into glucose and enters the bloodstream, resulting in a rise in the blood glucose level. Pure glucose has a GI of 100 and serves as a reference point to which all carbohydrate foods are compared. A food that has a GI of 55 or over is regarded as high GI and food that has a GI of less than 55 is regarded as low GI (The University of Sydney, 2017).

Figure 5 shows the change in blood glucose levels over time in response to the intake of high and low GI foods. Click on High GI and Low GI for an explanation of each one.

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Figure 5 Blood glucose levels over time in response to low and high GI food
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Some examples of high, moderate and low GI foods are shown in Table 2.

Table 2 High, moderate and low glycaemic index foods
High GI Moderate GI Low GI
Glucose 100Cornflakes 81Potato (boiled) 56
Parsnips 97Chips 75Sweet potato 54
French baguette 95Bagel 72Bananas 52
Lucozade Original 95Watermelon 72White pasta 50
Honey 87Wholemeal bread 71Muesli 49
Potato (baked) 85White bread 70Porridge oats 49
Sports drinks 70Baked beans 48
Weetabix 66Apples 38
White rice 64Yogurt 36
Shredded Wheat 64Chickpeas 28
Raisins 64Whole milk 27
Cherries 22
Fructose 20
(Source: Adapted from Bean, 2006)