What does glycaemic index mean?
Glycaemic index (GI) is a measure of how quickly a food raises blood sugar compared with pure glucose. Foods with a low GI produce a steadier rise in blood sugar, while foods with a high GI cause a faster, sharper rise.
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What is this?
Glycaemic index is a scale from 0 to 100 where pure glucose is set at 100, and other foods are ranked by how much they raise blood sugar over the following two hours after eating, compared with the same amount of carbohydrate from glucose. Foods are generally grouped into low GI (under 55), medium GI (56–69) and high GI (70 and above).
GI is affected by several factors, including fibre content, cooking method, ripeness and what the food is eaten with. For example, an overripe banana has a higher GI than an unripe one, and pasta cooked al dente has a lower GI than overcooked pasta.
Why does it matter?
Glycaemic index is useful because steadier blood sugar swings can support better satiety and more stable energy through the day, and is especially relevant for people with diabetes or impaired glucose tolerance. At the same time, GI is just one of several factors to consider when assessing how healthy a food is overall.
Good sources
Combine carbohydrates with protein and fat
This lowers the overall glycaemic response of a meal, even if an individual food has a high GI.
Choose whole grain versions
Whole grain products usually have a lower GI than refined versions due to higher fibre content.
Look at glycaemic load, not just GI
Glycaemic load also accounts for the amount of carbohydrate in a portion, and often gives a more practical picture.
Don't let GI override everything else
Some high-GI foods, like watermelon and boiled potatoes, are still nutritious and healthy in moderate amounts.
What does the research say?
Studies show that diets with a lower average glycaemic index can support better blood sugar control in people with type 2 diabetes and somewhat better satiety in some studies. Research still suggests, however, that the effect on weight and long-term health in healthy people is more modest than GI-based diets have often claimed.
Some researchers point out that glycaemic load, which accounts for both GI and the amount of carbohydrate in a normal portion, gives a more clinically relevant picture than GI alone, since GI is measured using standardised amounts that don't always reflect typical portion sizes.
Common misconceptions
«Low GI automatically means a food is healthy.»
Some low-GI foods, like chocolate or potato chips, are still not nutrient-dense choices — GI says nothing about overall nutritional content.
«High GI means a food should be avoided entirely.»
Foods like boiled potatoes and watermelon have a high GI but are still nutritious and can safely be part of a healthy diet in normal amounts.
«GI is fixed and never changes for a given food.»
GI can vary depending on ripeness, preparation and what the food is combined with in a meal.
Who should pay extra attention?
- People with diabetes may benefit from learning about GI, but should also follow individual guidance from a healthcare provider.
- GI is measured on individual foods and doesn't always reflect how a whole mixed meal affects blood sugar.
- Focusing solely on GI can lead to overlooking other important factors like fibre, saturated fat and salt content.
- Individual blood sugar responses to the same food can vary from person to person.
Frequently asked questions
Does whole grain bread always have a low GI?+
Not necessarily — it depends on how finely the flour is milled and how much whole grain the product contains, so it can vary between brands.
Are low-GI diets good for weight loss?+
Some studies show a small benefit for satiety, but overall low-GI diets don't show clearly better weight results than other balanced diets over time.
What's the difference between GI and glycaemic load?+
GI measures the quality of the carbohydrate, while glycaemic load also accounts for the amount of carbohydrate in a typical portion, giving a more practical picture.
Keep reading
Carbohydrates
Carbohydrates are the body's main energy source and are found in everything from fruit and vegetables to bread, pasta and sugar. The quality of the carbohydrate source matters far more for health than the amount alone.
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Fibre
Fibre comes from plants and plays a key role in digestion, blood sugar regulation and a healthy gut microbiome. Most people in Norway eat less fibre than recommended, and it is often one of the easiest places to start when improving your diet.
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Protein
Protein is the building block of muscles, skin, enzymes and hormones, and one of the nutrients that gives the most satiety. Most people get enough protein through a varied diet, but needs can shift with age, activity level and life stage.
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No two people are alike.
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