The glycemic index or GI is a number from 0 to 100 assigned to a food, which represents the relative rise in the blood glucose level two hours after consuming that food.

The GI of a specific food depends primarily on the quantity and type of carbohydrate it contains; but also is affected by the amount of entrapment of the carbohydrate molecules within the food, the fat and protein content of the food, the amount of organic acids (or their salts), and whether it is cooked and if so how it is cooked. A food is considered to have a low GI if it is 55 or less; high GI if 70 or more; and mid-range GI if 56 to 69. Diet management according to GI is essential for fitness particularly for people suffering from diabetes or over age of 35.

 Here's a division of food as per the GI. This information on GI  would help you make wise and healthy choice of food 

Some  Low GI snacks to stock-up on