Glycemic Index and Glycemic Load

The glycemic index (GI) rates a carbohydrate food by how much it raises blood glucose over 2 hours compared with a reference (pure glucose or white bread = 100). General bands: low ≤55, medium 56–69, high ≥70. High-GI foods (white bread, potatoes, sugary drinks) spike glucose quickly; low-GI foods (most legumes, whole fruit, oats, pasta) raise it slowly. Fiber, fat, protein, acidity, and cooking/processing all shift a food's GI (see fiber).

Glycemic load (GL) improves on GI by accounting for the amount of carbohydrate in a realistic serving: GL = (GI × grams of carbohydrate per serving) ÷ 100. This corrects misleading cases — watermelon has a high GI but a low GL because a serving holds little carbohydrate.

Where it's useful:

• Diabetes/blood-sugar management: favoring lower-GI/GL choices can smooth glucose response (see diabetes-exercise).
• Endurance fueling: higher-GI carbohydrate speeds glycogen restoration after exercise, while lower-GI pre-exercise meals give steadier energy (see carbohydrate-timing).

Caveats: GI is measured for single foods eaten alone; mixed meals behave differently, and many low-GI foods (e.g., ice cream, due to fat) aren't "healthy." GI is one lens — overall diet quality, fiber, and total calories matter more than chasing low GI per se.

• GI ranks blood-glucose rise vs. reference: low ≤55, medium 56–69, high ≥70.
• GL = GI × carb grams per serving ÷ 100 (accounts for portion).
• High-GI aids post-exercise glycogen refill; low-GI gives steadier pre-exercise energy.
• Useful for diabetes/blood-sugar management.
• Mixed meals differ from single-food GI; whole-diet quality matters more.

• carbohydrates — GI describes carbohydrate quality.
• fiber — fiber lowers a food's glycemic response.
• carbohydrate-timing / endurance-fueling — GI in exercise fueling.
• diabetes-exercise — GI/GL in glycemic management.