What is the Difference Between Glycemic Index and Glycemic Load?

Understanding the difference between glycemic index and glycemic load is important for anyone who needs to lose weight, including children. But first, it is important to understand the definition of the two terms.

Definition of Glycemic Index: The glycemic index, abbreviated as 'GI', is a calculation of how specific carbohydrate rich foods affect blood sugar levels over a period of 2 hours. Foods containing simple carbohydrates are easier to digest and have the highest glycemic index. Complex carbohydrates burn slower and therefore have a lower GI.

Wheat Bread

Definition of Glycemic load: The glycemic load, abbreviated as 'GL', is a ranking system for carbohydrate content in food portions based on both their glycemic index (GI) and portion size.

Scientists calculate glycemic index by providing 10 individuals a 50 gram serve of the food to be tested then measuring their blood glucose response over the next two hours. This response is compared to the blood sugar response to glucose and averaged across the 10 test subjects to calculate a relative index value.

The problem with this approach is that in real life, portion sizes vary from child to child. Not every child consumes a 50 gram portion! So glycemic index doesn't provide an accurate measure of the effect of any given food on blood sugar levels.

For this reason, the glycemic load is considered to provide a more accurate measure than the glycemic index alone since it takes portion size into account.

The metric formula to calculate the glycemic load of food is: GI value x usable carb content (in grams), divided by 100.

The imperial (UK and US) formula to calculate the glycemic load of food is: GI value x usable carb content (in oz), divided by 100 x 28.4. Note that this figure isn't exact since the original formula was created in metric but it provides a reasonably accurate indication.

Say for example you want to calculate the GL of two slices of white bread made from wheat flour. The glycemic index of one 30 gram (1 oz) slice of bread is 69. Since children generally eat two slices of bread we need to calculate it according to two slices. The usable carbohydrate content of one slice of white bread is 14 grams (15 grams minus 1 gram of dietary fiber). Therefore, to calculate the glycemic load for two slices of bread the sum is:

Metric: (GI)69 x (Carbs)28 / 100 = 19.32

Imperial: (GI)69 x (Carbs)0.99 / 100 x 28.4 = 19.40

The ranges for glycemic index are

Low GI = 55 or less
Medium GI = 56-69
High GI = 70 or more

The ranges for glycemic load are

Low GL = 10 or less
Medium GL = 11-19
High GL = 20 or more

Okay, lets compare the glycemic load of different types of bread:

Two slices of white bread have a GL of 19
Two slices of whole wheat bread have a GL of 15
Two slices of multi grain bread have a GL of 10

As you can see from this, the glycemic load of two slices of white bread squeezes into the medium glycemic load range. If a child consumes four slices per meal the figure increases to 38 which makes it high GL. On the other hand, the glycemic load of multi grain bread is barely half that of white bread so four slices of multi grain bread has a GL of 20 which is much better. Remember, the higher the dietary fiber content the lower the glycemic load. This is one of the reasons why it is important to provide your child with wholegrain products rather than simple, processed carbohydrates like bread or pasta made from white flour and white rice.

But why should children consume low GL foods? Foods with a high GL tend to cause a surge in blood sugar levels followed by an equally rapid drop which triggers the child's appetite. If the energy generated is not required it can be converted to fat storage. In diabetics this can cause dangerous fluctuations in blood sugar levels. Low GL foods do not cause this surge, take longer to digest, provide lasting energy and satisfy the hunger for longer which assists with weight loss. Consuming low GL foods means that your child's overall calorie consumption can be reduced without them feeling hungry.

NOTE: A child should never consume food less than an hour before bedtime as this makes them more likely to store unused energy as fat.

If your child needs to lose weight then you need to understand the difference between glycemic index and glycemic load so you can provide them with low GI foods to satisfy their hunger for longer and stop them from constantly wanting to eat.

What is the Difference Between Glycemic Index and Glycemic Load?

Julia Bell is a student of nutrition and understands the challenges of providing a positive role model to children and guiding them to develop healthy eating and exercise habits. Her years of knowledge, insightful views and sometimes humorous anecdotes regarding child health, nutrition and weight loss can be found at http://weightlosstips4kids.com.

Receive a FREE kids weight loss package including THREE products by visiting her Kids weight loss blog.

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