Glycemic load answers the question GI can't: how much will this actual serving move my glucose? It is calculated by multiplying a food's glycemic index by the grams of available carbs in the serving, divided by 100. The standard bands: low is 10 or below, medium is 11–19, high is 20 and above.
Watermelon is the classic example of why GL exists. Its GI is a scary 76 — but a cup only holds about 11 g of available carbs, so its GL is a mild 8. Meanwhile spaghetti's GI is a gentle 49, but a big restaurant portion carries so many carbs that its GL lands solidly high. GI is speed; GL is speed times quantity, which is much closer to what your CGM actually shows.
For day-to-day use:
- A high-GI, low-GL food (watermelon, carrots) usually means a quick but small bump.
- A low-GI, high-GL food (a mountain of pasta) means a slow but big and long rise.
- Doubling the portion doubles the GL — it is the number that punishes eyeballed servings.
GL rewards the habit that matters most anyway: knowing what a real portion of a food looks like. The label on the food is fixed; the serving on your plate is the part you control.
