The Glycemic Index (GI) compares foods based on how rapidly they raise blood sugar after eating. Pure glucose = 100 (reference).
GI Categories
- Low GI (≤55): Oats, legumes, most fruits — steady energy
- Medium GI (56–69): Brown rice, whole wheat bread
- High GI (≥70): White bread, white rice, potatoes — rapid spike
Glycemic Load
GI doesn't account for portion size. Glycemic Load (GL) = GI × carbs per serving / 100. Watermelon has high GI (72) but low GL (4) because it's mostly water.
Cooking and Ripeness Change GI
The same food can have a different GI depending on preparation: al dente pasta has a lower GI than overcooked pasta, and ripe bananas have a higher GI than unripe ones. Cooling cooked starches (like rice or potatoes) after cooking also lowers their GI by forming "resistant starch."
GI in Context of Overall Diet
Low-GI foods are generally associated with better blood sugar control and satiety, which matters most for people managing diabetes or insulin resistance. For most healthy eaters, overall diet quality, fiber content, and portion size matter more than obsessing over any single food's GI number.