What is Glycemic Index?

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glycemic index cake

Many people with diabetes have a misconception that it is essential to completely avoid eating sugar, starch or any kind of sweet foods. In fact, carbohydrates are the major source of energy in the body and excessive suppression can lead to a greater desire for “sugar.” Most diabetic patients place a focus on reducing calories intake in their diet, but their biggest enemy is actually foods with a high glycemic index (GI), which can lead to blood glucose spikes after meals. This article will help you understand the functions and applications of GI.


Definition of Glycemic Index

Glycemic index (GI) is a measure of the rate of blood sugar rise after eating carbohydrate-containing foods, usually on a scale of 0-100. Glucose is used as a reference food, with a GI score of 100.


Foods with a high glycemic index will quickly raise blood sugar and be converted to provide energy. However, this energy is usually short-lived, and hunger may revisit very soon, easily leading to over-eating and weight gain. On the other hand, foods with a low glycemic index have a slower and more stable influence on blood sugar. These foods provide greater and longer-lasting satiety and more stable sources of energy, hence facilitating the reduction in food intake and body weight maintenance.


Examples of high, medium, low GI foods

The Glycemic Index Foundation classifies the GI of foods into 3 categories:

  • High GI foods (score: 70 or above): white rice, porridge, white bread, sweet bun, mashed potato, white sugar, watermelon, etc.
  • Medium GI foods (score: 56-69): brown rice, wheat bread, rice noodle, udon, papaya, mango, etc.
  • Low GI foods (score: 55 or under): oat, barley, soba noodle, vermicelli, pasta, dry beans, apple, orange, kiwi, etc.


Furthermore, glycaemic load (GL) is often taken into account to calculate the total amount of carbohydrate present per serving of your food. GL is calculated with the following equation: GI amount of carbohydrate (in grams) per serving 100. It is a realistic and accurate measure because normally in a meal, we eat a combination of foods with different GI values.

What factors affect GI?

Generally speaking, the easier the carbohydrate in foods to be metabolized into simple sugars, the higher the GI of the foods, and vice versa. The following are some factors that affect the GI of foods:


Cooking and processing of food

Some processed, refined food products or foods that have been cooked for a long time tend to have higher GI because they break down faster during the digestion process and release the simple sugar into the blood in a shorter time. These foods bring about a blood sugar spike. Examples include porridge, white bread, mashed potatoes, pureed fruit or juice.


Ripeness of food

Taking bananas as an example, their GI is about 30 when raw, but can rise to 51 after ripening. Size, texture, viscosity and other physical factors may also affect the GI of food.


Composition of food

Nutritional components of food, especially high fat, protein, soluble fiber, fructose (a carbohydrate found in fruits) and lactose (a carbohydrate found in milk and dairy products), also affect the GI of the food. Because the body needs more time to digest and absorb these nutrients, the release of sugar into the blood and thus the rise in blood sugar level would be delayed.


Other factors

Phytates (found in wholegrain bread and cereals), a storage form of phosphorus in plants, also slows down the rate of absorption of food and has a low GI.

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What are the benefits of a low GI diet?


Blood sugar control

A review produced by The American Journal of Clinical Nutrition stated that low GI diets can regulate blood sugar level and body weight in prediabetic or diabetic patients. Further research showed that low GI diets can improve gestational diabetes, a condition in which a non-diabetic woman develops high blood sugar level during pregnancy.


Weight loss

A low GI and low calories diet can bring about weight loss, in addition to regulating blood sugar level. Carbohydrates in low GI foods are digested and absorbed slowly in the body, effective in sustaining the sense of satiety and reducing the urge to eat. Appetite control in the long term promotes weight management.


Disease prevention

According to the International Carbohydrate Quality Consortium, a low GI diet is ideal for blood sugar control, which is effective in preventing and managing chronic conditions such as diabetes, obesity, cardiovascular diseases, stroke and even cancer.

Low GI meal plan

Here are some low GI meal options for your easy reference:



  • 2 slices of whole wheat bread + hard boiled egg + 1 cup of low-fat milk or 
  • Oatmeal + ¼ papaya + 1 cup of skimmed milk or 
  • Beef with rice noodles in tomato soup + 1 cup of low-sugar soy milk


  • Cauliflower rice with shrimp and seasonal vegetables + 1 bowl of corn soup or 
  • 1 bowl of cold soba noodles + 1 mixed vegetable salad + 1 tofu + 1 cup of green tea or 
  • ⅔ plate of (peeled) chicken rice (without sauce) + 1 bowl of vegetables (less oil) + 1 cup of orange juice


  • Chicken rice noodles + 1 bowl of vegetables + 1 kiwi fruit or
  • Roasted (peeled) chicken + 1 baked potato + salad or
  • Salted mackerel + 1 bowl of soba noodles + 1 mixed vegetable salad + 1 cup of green tea


  • 1 small banana or
  • 2 kiwi fruits or
  • 3 10g squares of dark chocolate


It may be tedious to browse for the GI of foods every single meal. A general idea is that low GI foods are usually of high fiber content and minimally processed. Keep in mind that it is more important to maintain a balanced diet than to focus on a particular aspect of it, i.e. carbohydrates in the diet.


Is high GI food all bad for your body?

Actually not. If you consume a small amount of high GI foods, the effect on blood sugar level is comparable to consuming a large amount of low GI foods. Furthermore, some high GI foods or fruits such as watermelon and pineapple can be healthy if consumed in moderate amounts. In a nutshell, the key to a healthy diet lies in the amount of consumption.

The lower the GI, the healthier the food?
Can a low GI diet promote weight loss?

This article was independently written by Healthy Matters and is not sponsored. It is informative only and not intended to be a substitute for professional medical advice, diagnosis or treatment. It should not be relied upon for specific medical advice.

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