What is GI (Glycaemic Index)?

Author: Amber Houghton   Date Posted:3 March 2014 

GI??? - The meaning behind the name

So you’ve heard “GI” tossed around by the media, seen it written on packaging and in the newspapers, but what is GI?


Well, GI stands for “Glycaemic Index”.  This refers to a food’s effect on blood sugar levels.  After you eat carbohydrate-based foods, your blood sugar levels rise.  However, not all carbohydrate-based foods are created equally; different types of carbohydrate-containing foods have various impacts on blood sugar levels. 

A food’s GI is determined by a range of factors, including:

  • The rate of digestion of the carbohydrate;
  • The rate at which the food is released from the stomach into the small intestine.  This can be influenced by the presence of soluble dietary fibres or acids, both of which slow the emptying the stomach;
  • The types of sugars contained;
  • The presence of fat;
  • The presence of proteins, as they impact upon hormone levels, especially insulin.



Since there are varying effects on blood sugar levels, the GI compares the impact of a particular food on blood sugar levels to that of a reference, often glucose. 

The food receives a score (the GI), which normally ranges from 20 to 90 for carbohydrate-based foods.  The GIs are generally divided into three classes:

  • Low GI foods- GI<55
  • Medium GI foods- 55≤GI≤70
  • High GI foods- GI>70


Written by Amber Houghton
Amber Houghton

Amber holds a Bachelor’s Degree in Naturopathy, and has a particular passion for nutritious, whole-food eating. She feels education surrounding the best dietary and lifestyle choices are fundamental in allowing people to take responsibility for their own health, and to help with the maintenance of their well-being.

Although passionate about wholesome food, Amber does confess to having a particular fondness for cake, and enjoys a slice every now and then.