The glycemic index of a food indicates how a food will affect blood sugar and insulin after you eat it. A low glycemic index number, or less than 55, means that the food will raise blood sugar and insulin levels less than one that is higher on the index scale of 0 to 100. Many fast foods -- such as burgers, sandwiches, potatoes, sweetened soft drinks and desserts -- have a medium glycemic index, which is 56 to 69, or a high glycemic index, which is 70 or greater.
A food must contain some sort of carbohydrate or source of sugar to register on the glycemic index. Foods like meat or fats do not register on the index. The glycemic index of a fast-food sandwich is most heavily influenced by the size of the bun or bread. A fried fish sandwich with cheese and tartar sauce has a glycemic index of 56 to 76 on a scale of 100. A hamburger with ketchup, onion, pickles and mustard on a bun has a glycemic index of 58 to 74. A fried chicken patty on a bun with lettuce and mayonnaise has a similar glycemic index to other sandwiches at a level of 63 to 69. According to the American Diabetes Association, choosing a 100 percent whole-grain bun for your fast-food sandwich could lower the glycemic index below 55, making it a low-glycemic-index food.
Potatoes, fried and baked, have one of the highest glycemic indexes of all fast foods. A large serving is measured at 64 to 76 on the glycemic index, making it a medium- to high-glycemic-index food. An average serving of a baked potato measures at 111, which is higher than the reference value of the glycemic index, glucose, that registers at 100. A side of macaroni and cheese, about 1 cup, has a glycemic index of 64. Healthy side orders that have a low glycemic index include fruits and nonstarchy vegetables like a lettuce salad.
Beverages and Smoothies
Beverages can be one of your highest sources of simple sugars. A cup of a common cola soft drink may yield a rating of 63 on the glycemic index scale. Lemonade has a range of 49 to 59 per 1-cup serving. Smoothies have a lower glycemic index than cola or lemonade because they may contain some fiber if made from whole fruit. A cup of banana smoothie has a glycemic index of 26 to 34, which makes it low on the glycemic index and may be your best bet apart from water or unsweetened tea or coffee.
Desserts and Sweets
Desserts and sweets may have a high glycemic index due to the high amount of simple sugars. For example, a doughnut that is around 3 inches in diameter has a glycemic index of 68 to 82, which puts it on the upper end of the index. The glycemic index of a low-fat vanilla ice cream is 46 for less than 1/2-cup serving, which makes it a low-glycemic-index choice if you want to have something sweet.