Glycemic load is a number indicating how food affects sugar levels, but not only how fast, but also how high those levels go up. That is how it differs from glycemic index that shows the speed of blood sugar spikes and depends on the quality of carbohydrates, while glycemic load depends on the quantity as well. Some foods can have high glycemic index for example, but low glycemic load, meaning they cause fast rise, but they contain very little sugars.