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Introduction to the Glycemic Index

When I was first started paying more attention to my health, I remember reading many articles encouraging those who were watching their weight to consume foods that have a lower glycemic index (GI). 

Most of us are probably familiar with what foods are considered low GI or high GI. If you scroll through your instagram feed, you’ll probably see your favourite health and fitness influencers creating recipes featuring low GI foods. This is probably because these foods are touted for their weight loss properties. But have you wondered what the glycemic index is? And how is it related to your health? Does it actually have any impact on you at all?


The glycemic index measures the rate at which a food increases sugar levels in the blood. It was created by Dr David Jenkins as a helpful dietary tool for the management of diabetes and dyslipidemia. The glycemic index is applied to foods that contain carbohydrates (e.g. rice, legumes, pasta, bread, etc.), and used to understand how they affect our blood sugar levels.

There are many types of carbohydrates that are found in our food, and in our blood. However, the glycemic index measures glucose – a simple carbohydrate, which is the most abundant monosaccharide (a single unit of carbohydrate). It is the main energy source for our bodies and it is part of many metabolic pathways. 

The glycemic index is used as a tool to attempt to understand the effects of different carbohydrates on glucose levels in blood, because our body responds to spikes in blood glucose by releasing insulin.

Insulin is a hormone released by the pancreas that helps to regulate blood glucose levels. It prevents blood glucose levels from getting too high. It does so by allowing the body to use, or to store, glucose for future use.


Carbohydrates in food sometimes exist as many units of different types of monosaccharides, connected together by bonds. They form long chains, or have different structures – but there are an infinite number of different combinations that exist. Sometimes they exist as single units, such as in simple sugars. The structure of carbohydrates, it’s make up, complexity and how large it is all give rise to different properties. For instance, it also contributes to how easily it is broken down.

For example, simple sugars are easy to break down and the monosaccharides are more quickly absorbed. This is because the carbohydrates in it are small, and there are not many bonds to break down. Hence, when you eat simple sugars without any protein or fat (we’ll go through this in the next article), your blood sugar levels will increase very quickly.

If a certain food is considered low GI (glycemic index of lower than 55), this means that it is digested at a slower rate, therefore glucose is absorbed by the small intestines, and into the bloodstream, more slowly.

Digestion involves little units typically made up of proteins, called enzymes. These enzymes speed up the process of digestion and the breaking of bonds between molecules to allow the small intestine to absorb nutrients into the bloodstream. When digestion is slower, it takes more time for the enzymes to break the bonds between units of micronutrients (like glucose, proteins, etc.). Therefore, the uptake of glucose into the bloodstream is also slower. This translates into a slower and lower increase in blood sugar levels overall, and as a result, insulin response is comparatively smaller as opposed to higher GI foods.


Low GI foods are touted for their supposed tendency to aid in weight loss, as they are thought to cause satiation for a longer time due to the slower release of glucose. More importantly, some studies show that low GI diets could improve insulin resistance, as well as lowering glucose, cholesterol and triglyceride levels in individuals suffering from type 2 diabetes. Many diabetics adopt a low GI diet because of these benefits.

However, if you’re an athlete who undergoes a prolonged period of rigorous training, high GI foods may be useful to you! Consuming high GI foods ensures your blood sugars will not drop too low, which leads to hypoglycemia. There is also a suggestion that this practice may aid muscle recovery.

For examples of foods with their different glycemic index values, click here.


There is so much emerging research regarding the glycemic index, and with this research, there are questions on how applicable it is to you and me. There is also another indicator called glycemic load to take into account portion size. Since we don’t typically eat carbohydrates without any other macronutrient groups, including these also changes how your blood sugar rises in response to a meal.

I’ll be breaking down these different concepts in the next few articles!


Glycemic Load and how combining carbohydrates with other macronutrients changes its effect

[a list of references will be included in the final article]

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