Glycemic index vs glycemic load
Glycemic index tells you how fast a carbohydrate raises blood sugar. Glycemic load tells you how much the portion you actually eat raises it. For everyday decisions, glycemic load is usually the more useful number.
The formula
Glycemic load = GI × available carbohydrate in the portion (g) ÷ 100
Available carbohydrate is total carbohydrate minus fiber. For example, a medium 120 g apple has a GI of 39 and about 14 g of available carbohydrate: 39 × 13.7 ÷ 100 ≈ 5.
| Glycemic load | Per serving | Per day |
|---|---|---|
| Low | 10 or less | under 80 |
| Medium | 11 to 19 | 80 to 120 |
| High | 20 or more | over 120 |
You can run the numbers for any food and amount with the glycemic load calculator.
When GI and GL disagree
The interesting cases are foods with a medium or high GI but little carbohydrate per serving, and the reverse:
| Food | GI | Serving | GL |
|---|---|---|---|
| Cantaloupe | 65 | 120 g | 6 |
| Carrots | 32 | 80 g | 1 |
| Pumpkin | 53 | 80 g | 2 |
| Popcorn | 62 | 20 g | 8 |
| Spaghetti | 47 | 180 g | 25 |
| Dates | 54 | 60 g | 22 |
| White rice | 72 | 150 g | 30 |
| Jasmine rice | 89 | 150 g | 37 |
- Cantaloupe and pumpkin have a medium GI, but they are mostly water, so their glycemic load is low.
- Pasta has a low GI, but a big plate carries a lot of carbohydrate and a high load.
- Dates are low-to-medium GI, but so dense in sugar that a few of them add up to a sizable load.
Which one should you use?
Both. GI helps you choose which carbohydrate to eat among similar options; glycemic load helps you decide how much. A practical rule: pick low- or medium-GI carbohydrates and keep each meal's load low to medium by adding protein, vegetables and healthy fats.
The glycemic load of a whole plate is the sum of each ingredient's load. The Glycemic Index AI Food Scanner app estimates it automatically from a photo.
Sources
- Atkinson FS, Brand-Miller JC, Foster-Powell K, Buyken AE, Goletzke J. International tables of glycemic index and glycemic load values 2021: a systematic review. Am J Clin Nutr. 2021;114(5):1625–1632.
- ISO 26642:2010. Food products — Determination of the glycaemic index (GI) and recommendation for food classification.
