Explanation:

Values range from 1 (the slowest) to 100 (the fastest, the index of pure glucose). However, how quickly the level actually increases also depends on what other foods are ingested at the same time and other factors.
The glycemic index tends to be lower for complex carbohydrates than for simple carbohydrates, but there are exceptions. For example, fructose (the sugar in fruits) has little effect on blood sugar.
The glycemic index is thought to be important because carbohydrates that increase blood sugar levels quickly (those with a high glycemic index) also quickly increase insulin levels.
The increase in insulin may result in low blood sugar levels (hypoglycemia) and hunger, which tends to lead to consuming excess calories and gaining weight.
Carbohydrates with a low glycemic index do not increase insulin levels so much.
As a result, people feel satiated longer after eating. Consuming carbohydrates with a low glycemic index also tends to result in more healthful cholesterol levels and reduces the risk of obesity and diabetes mellitus and, in people with diabetes, the risk of complications due to diabetes.