The Glycaemic Index Explained

The glycaemic index (GI) is a ranking of how quickly carbohydrate foods raise your blood sugar. Low-GI foods raise blood sugar slowly and steadily. High-GI foods raise it quickly. That single concept has quietly reshaped how dietitians, diabetes educators and sports nutritionists think about carbohydrate choice.

But the glycaemic index is also one of the most misunderstood ideas in nutrition. The number on a packet does not tell the whole story. A food’s GI depends on ripeness, processing, what you eat it with, how long you cook it, and even the time of day you eat it. Used properly, the GI is a useful tool. Used badly, it leads to decisions that have little effect on your blood sugar or your weight.

This article explains the glycaemic index the way a dietitian would explain it to a patient: what it actually measures, when it matters, and when it does not.

What you will learn:

• How the GI is calculated and what the numbers actually mean
• The critical difference between glycaemic index and glycaemic load, and why load is often more useful
• Which foods are low, medium and high GI, with practical examples from the Australian diet
• How combining foods (fat, protein, fibre, acid) changes the glycaemic response
• When GI matters most: diabetes, prediabetes, sports performance, weight management
• When GI is over-emphasised and you can safely ignore it

Written by an Accredited Practising Dietitian. The full article is a practical, evidence-based breakdown, not a fad-diet explainer.