Why glycemic load is more useful than glycemic index alone
Glycemic index (GI) measures how quickly 50 g of available carbohydrate from a food spikes blood glucose, on a 0–100 scale. Glucose itself sits at 100. The number ignores serving size — so foods like watermelon (76) look identical to white bread (75) on the GI list, even though a slice of bread has three times the carbs of a watermelon serving. Glycemic load fixes this: GL = (GI × g of available carbs) / 100. It captures both the speed of the spike and the area under the curve.
Low / medium / high bands
Per Sydney University’s GI Foundation: GL of 10 or less per serving is low; 11–19 is medium; 20+ is high. For a typical day on a 2000-kcal diet, a daily total below 100 GL is consistent with low-GL eating; for type-2 diabetes and prediabetes, registered dietitians often target below 80.
How to lower the GL of a meal you already love
Three simple swaps: add protein and fat (slows gastric emptying — pairing rice with paneer or egg drops the meal GL by 20–30%); choose less-ripe fruit (a green banana is GI 30, an overripe one GI 60); favour cooked-and-cooled starches (resistant starch in cooled potato or pasta resists digestion and lowers the effective GL).
Limits
GI varies ±10 between published studies — ripeness, milling, starch retrogradation and individual gut microbiome all shift the response. Use GL for relative comparison (“is this meal heavier than that one?”), not as a strict prescription. For type-1 diabetes, carb counting (not GL) drives insulin dose decisions.
Sources
- Atkinson FS et al. International tables of glycemic index and glycemic load values 2021. Am J Clin Nutr. 2021;114(5):1625-32.
- University of Sydney Glycemic Index Foundation. About Glycemic Load.
- Diabetes Canada. Clinical Practice Guidelines: Nutrition Therapy.