Glycemic Index & Load

What is Glycemic Index?

The glycemic index is a scale that ranks the number of carbohydrates in foods from zero to 100, indicating how quickly a food causes a person’s blood sugar to rise. Foods high on the glycemic index (GI) can cause harmful blood sugar spikes in people with diabetes.

The GI values can be broken down into three ranges.

Low GI: 55 or less
Medium GI: 56 to 69
High GI: 70 to 100

Some common foods and their GI can be found at this link: Glycemic Index Chart for Common Foods (verywellhealth.com) and Glycemic index of Indian foods (myupchar.com).

meal plan

What is Glycemic LOAD?

The glycemic load (GL) of food is a number that estimates how much the food will raise a person's blood glucose level after eating it. One unit of glycemic load approximates the effect of eating one gram of glucose. Glycemic load accounts for how much carbohydrate is in the food and how much each gram of carbohydrate in the food raises blood glucose levels. Glycemic load is based on the glycemic index (GI), and is calculated by multiplying the grams of available carbohydrate in the food by the food's glycemic index, and then dividing by 100.

GL is worked out by the following formula:

GL = GI x carbohydrate / 100

To work with this equation, you will need to know:

The Glycemic Index (GI) of the food found by referring to a table of Glycemic Indexes for different foods
The amount of carbohydrate in that quantity of food

Example Calculations

Another example: Jim is going to have roast chicken for dinner and is thinking of having it either with white rice or couscous.

Jim has enough white rice to make a 130g (when cooked) portion of rice which will provide 40g of carbohydrate. White rice has a Glycemic index value of 85. He also has enough couscous to make a 200g serving of couscous which will also provide 45g of carbohydrate. Couscous has a Glycemic index value of 60.

Glycemic load of white rice portion
= GI x carbohydrate / 100
= 85 x 40 /100
= 34

Glycemic load of couscous portion
= GI x carbohydrate / 100
= 60 x 45 /100
= 27

So, Jim sees that even though the smaller portion of white rice has less carbohydrate, the portion of couscous actually has a lower Glycemic load. The Glycemic load calculation tells Jim that the portion of couscous, despite being larger and containing slightly more carbohydrate, is less likely to cause as sharp a rise in his blood sugar levels as the portion of white rice.

Example: What is the Glycemic load of a slice of whole grain bread?

Glycemic Index of whole grain bread = 45
Carbohydrate content of a slice of bread = 18g

Note these figures are examples.

The GI and carbohydrate values may vary slightly between different types and slice sizes of whole grain bread.

The final answer for the glycemic load is 8.1

Making use of both

Glycemic Load

Glycemic load involves calculation - which may not be practical for everyone.

However, those with time for the calculations will find it a helpful extra tool in choosing which foods and portions are suitable for maintaining good blood glucose levels.

It can be particularly useful in assessing the impact of a certain meal on your blood glucose levels - especially if you have a specific meal quite often or are trying a new meal.

Different people with diabetes will have different tolerances to carbohydrates in food. Some may comfortably tolerate meals with a medium GL whereas others may only tolerate low GL values.

If you have access to blood glucose testing supplies, you may wish to test which values allow you to keep your sugar levels within the recommended guideline blood glucose values.

A good way to assess this is to test your blood glucose before eating, 2 hours after eating, and again 4 hours after eating.

Glycemic Index Comparison

Food ranked high on the GI may represent a huge portion of a food because GI is not based on standard serving sizes.

If a food is ranked high on the glycemic index it has readily available carbohydrates for quick absorption.

However, the same food can have a low glycemic load because there may not actually be much total carbohydrate in a given serving of that food. A low GL is the better indicator that a food won't have much impact on blood glucose levels.

Here are two examples:

Watermelon has a high GI of 72, yet a low GL of 7.21. The high GI is based on 5 cups of watermelon, not an actual serving size of 1 cup. The low GL means one serving of watermelon doesn't contain much carbohydrate, because it is actually mostly water.

2. Carrots are another example. Many people think carrots raise their blood sugar a lot - but it's not true. carrots have a high GI of 71, BUT the GL for carrots is only 6. Therefore, unless you're going to eat a pound and a half of carrots in one sitting, an average serving of carrots will have very little impact on blood glucose levels. That said, juicing carrots - consuming more carrots at once - will have a greater impact on blood glucose.

Overall Round Up

Everyone can benefit by eating a balanced diet of protein and fat, and foods that are lower on the GL and GI index.

Foods with a lower GL and GI typically are high in fiber and nutrients and sustain your energy better throughout the day.

Also, knowing the GL of a food is a better indicator of whether that food will cause your blood sugar to spike.

When your blood sugar spikes, the body releases extra insulin to bring down your blood sugar. If your body is asked to release extra insulin on a regular basis, it begins to lead to insulin resistance for many people and diabetes - especially if diabetes is in your family.

Consuming low GL and GI foods keeps us satiated longer because these foods are more slowly broken down for glucose utilization. The result is that you feel fuller for longer.

When you consume high GL and GI foods, blood sugar levels spike which causes a short-term feeling of fullness.

But then blood sugars plummet which causes you to crave food again and you ultimately end up consuming excess calories, which contributes to weight gain.

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