It is measured depending on the type of nutrients each type of food provides and on how they have been processed:
-FAT.- Those foods which contain both fat and carbohydrates have a lower glycemic index than the ones without fat contents, for example, chocolate.
-FIBRES.- The higher the fibre content (especially soluble fibre), the lower the GI, for example, oat and fruits.
-PROTEIN.- High protein contents in foods tend to moderate their GI. For example, legumes such as soy, peas, etc.
According to how carbohydrates are processed:
-Grain thickness.- The thinner and more refined the grind, the higher the IG.
-Treatment and gelling process.- The more processed, the higher the GI.
-Mixes and presentation.- If a mix has more starch and less flour, it will have a higher GI.
-Preparation and cooking process.- The more foods are heated, cooked, baked or boiled, the higher the GI.
-Ripening process.- The riper the fruit, the higher the GI.
-Preserving.- The longest the shelf life of a product, the higher the GI.
So it is quite simple: we need to consume less processed foods and more fresh foods.