Glycemic index

In nutrition, the glycemic index is a "numerical system of measuring the rate of blood glucose generation by a particular food item as compared to a reference item, such as glucose = 100.  Foods with higher glycemic index numbers create greater blood sugar swings.  These numbers do not correspond to calories or amounts of food intake but  rather, depend on the rates of digestion and absorption of these food items."

Physiology
"The glycemic index factor is a ranking of foods based on their overall effect on blood sugar levels. Low glycaemic index foods, such as lentils, provide a slower more consistent source of glucose to the bloodstream, thereby stimulating less insulin release than high glycaemic index foods, such as white bread."

The glycemic load is "the mathematical product of the glycemic index and the carbohydrate amount".