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Glycaemic Index

Every carbohydrate food that we eat has a certain amount of sugars, some natural and some refined (added). In order for us to ascertain how quickly the sugars from that food will release into our blood stream, scientists have developed a system that will inform us of how quickly this will occur. This is called the Glycaemic Index.

The Glycaemic Index was developed by Dr. David Jenkins and his colleagues in between 1980 and 1981 at the University of Toronto in their research to find out which foods were best for people with diabetes. The lower the score for the food, the slower the release of sugars into the blood stream, this means that the individual will have a lower Insulin response to work with the sugars resulting in less work for the Pancreas and better Insulin sensitivity. Using low GI foods has been shown to improve long-term blood glucose levels, improve weight control and reduce risks of type 2 diabetes.

The GI scale can be broken down into the following categories:

  • High GI (> 70)
  • Medium GI (56-69)
  • Low GI (< 55)

Glycaemic Load

Glycaemic load is a related measure to the Glycaemic Index (GI). It estimates how much the food will raise a persons blood glucose levels by after eating it. This is calculated by multiplying the carbohydrate content of the actual serving of the food by the GI divided by 100.

For example, a (fully ripe) Banana has a GI of 51 which has a ‘low GI’ value’ (because it is under 55) whereas a over-ripe banana with brown speckles has a GI of 48.

The total amount carbohydrate in the average medium banana has approximately 27g. This will calculate the GL to be:

27 x 51 / 100 = 13.77

This formula and calculation can be used for different foods but also complete meals and this will give a good reading on how much the meal or food will impact on the persons blood glucose.

Another example if this is Watermelon. Watermelon has a high GI (72) and has 5g of carbohydrates per serving. The calculation for this would be as follows:

5 x 72 / 100 = 3.6

The Glycaemic Load references are as follows:

  • High (> 20)
  • Medium (11-19)
  • Low (<10)

What does all this mean?

The relationship between GI and GL is clear; they have a direct approach to how our blood glucose levels rise and fall depending on the type of food consumed. By controlling our blood glucose levels we can ensure that we are at a reduced risk of diabetes, coronary heart disease, cardiovascular disease, strokes, angina and other life-threatening illnesses.

Research has shown that women who had a diet with high GI foods were 21% more likely to develop type 2 diabetes than women who had a lower GI diet (source – opens in new window).

In addition to the health benefits, a low GI and low GL diet has proven to help with weight control, particularly weight loss. This is due to the body not consuming too many sugars all at once. The lower your Insulin levels are in the blood stream then the lower amount of glucose your body has to use as energy and therefore will use adipose tissue (fat) to fuel your body.

GI Reference Table

Below is a reference table, broken down into high GI, medium GI and low GI.

Low GI Foods

Food GI
Roasted and salted peanuts 14
Low-fat yoghurt with sweetener 14
Cherries 22
Grapefruit 25
Pearl barley 25
Red lentils 26
Whole milk 27
Dried apricots 31
Butter beans 31
Fettucine pasta 32
Skimmed milk 32
Low-fat fruit yoghurt 33
Wholemeal spaghetti 37
Apples 38
Pears 38
Tomato soup, canned 38
Apple juice, unsweetened 40
Noodles 40
White spaghetti 41
All Bran 42
Chick peas, canned 42
Peaches 42
Porridge made with water 42
Lentil soup 44
Oranges 44
Macaroni 45
Green grapes 46
Orange juice 46
Peas 48
Baked beans in tomato sauce 48
Carrots, boiled 49
Milk chocolate 49
Kiwi fruit 52
Stoneground wholemeal bread 53
Crisps 54
Special K 54
Banana 55
Raw oatbran 55
Sweetcorn 55

Medium Glycaemic Index foods (56 to 69)

Moderate GI Foods

Muesli, non toasted 56
Boiled potatoes 56
Sultanas 56
Pitta bread 57
Basmati Rice 58
Honey 58
Digestive biscuit 59
Cheese and tomato pizza 60
Ice cream 61
New potatoes 62
Coca cola 63
Apricots, canned in syrup 64
Raisins 64
Shortbread biscuit 64
Couscous 65
Rye bread 65
Pineapple, fresh 66
Cantaloupe melon 67
Croissant 67
Shredded wheat 67
Mars bar 68
Ryvita 69
Crumpet, toasted 69
Weetabix 69
Wholemeal bread 69

High Glycaemic Index foods (70 or more)

Note: Swap these foods for those with a low GI value or eat them together with a low GI food. Having a jacket potato with baked beans, for example, will lower the GL value of that whole meal.

High GI Foods

Mashed potato 70
White bread 70
Watermelon 72
Swede 72
Bagel 72
Branflakes 74
Cheerios 74
French fries 75
Coco Pops 77
Jelly beans 80
Rice cakes 82
Rice Krispies 82
Cornflakes 84
Jacket potato 85
Puffed wheat 89
Baguette 95
Parsnips, boiled 97
White rice, steamed 98
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author: Tom

Tom has been in the fitness industry for over 8 years. He is qualified in functional movement, Kettlebells, Boxercise, Nutrition and many other qualifications. Tom is also the founder and director of ActivityX.

For more information on Tom, see his trainer profile.

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