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Glycemic index: how does it work?

Understand GI to choose carbs better without obsession.

Repas équilibré avec féculents, légumes et protéinesNutrition

A clear guide to the glycemic index

Why the glycemic index matters

The glycemic index (GI) measures how quickly a carb-rich food raises blood sugar. It helps compare foods, but it does not tell the whole story on its own.

A simple definition of GI

GI compares a food’s blood sugar response to a reference food (often glucose). The higher the GI, the faster blood sugar rises after eating.

The main GI categories

  • - Low GI: slower rise, steadier energy.
  • - Medium GI: moderate impact.
  • - High GI: quick spike.

    • Why GI varies for the same food

  • - Ripeness: a very ripe banana has a higher GI.
  • - Processing: the more refined, the higher the GI.
  • - Structure: whole vs blended vs juice changes absorption speed.

    • Cooking, texture, and cooling

  • - Long cooking makes starch more available → higher GI.
  • - Cooling some starches can lower GI.
  • - Texture (crunchy vs mashed) also affects absorption.

    • What you eat it with also matters

  • - Fiber slows digestion.
  • - Protein and fat reduce the blood sugar spike.
  • - A full meal often has a lower overall GI than a single food.

    • GI ≠ overall nutrition quality

    A low GI does not automatically mean “better” (some foods are low GI but high in fat). And some healthy foods have a higher GI. GI is a signal, not a verdict.

    What about glycemic load?

    Glycemic load (GL) considers both GI and the amount of carbs eaten. It is often a more realistic guide for a full meal.

    Reading labels the smart way

  • - Check sugars, but also the portion size.
  • - Compare similar products rather than different categories.

    • See our guide to better understand sugar

    Simple daily tips

  • - Prioritize whole grains and legumes.
  • - Add vegetables to every meal.
  • - Skip juice; choose whole fruit instead.
  • - Combine starches with protein and fiber.

    • Key takeaway

    GI is a helpful tool for understanding carbs, but it does not replace a balanced diet. If you have diabetes or a medical condition, consult a healthcare professional.

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