The glycemic index measures the effects of certain foods on the glucose level in your bloodstream. Many commercial diets today are based on the glycemic index, with the belief that controlling your blood sugar can lead to weight loss and other health benefits. Before you begin a low glycemic index diet or any other restrictive diet, talk with your doctor or a registered dietitian about the diet's possible dangers and benefits.
Description
The glycemic index is a comparison of the measurement of how much your blood glucose and insulin levels increase after eating a certain carbohydrate food versus a set amount of glucose. If a food causes your blood glucose level to increase quickly, it's classified as having a high glycemic index. Conversely, a food with a low glycemic index releases glucose slowly into your bloodstream. The glycemic index of glucose sugar is 100, and foods compared with glucose are ranked 0 to 100 depending on how quickly they affect your blood sugar level.
Significance
Low glycemic index diets are marketed for weight loss and blood sugar control, with the belief that consuming foods that rapidly increase blood glucose levels lead to poor insulin control and weight gain, according to MayoClinic.com. The Zone diet, Sugar Busters and Nutrisystem are among the most popular diets that use the glycemic index as a basis for weight loss. Low glycemic index diets emerged as a cross between low-carbohydrate and low-fat diets. Instead of eliminating or severely restricting carbohydrates in low-carb diets, the low glycemic index diets restrict certain carbohydrates that have a high glycemic index with an ultimate goal of reducing your body's production of insulin. Following a low glycemic index diet could potentially help you to lose weight, reduce your risk for heart disease and prevent or treat diabetes, according to the University of Pittsburgh. These claims are based on only preliminary scientific evidence, however.
Foods
Foods that have a ranking of 55 and below are considered to have a low glycemic index. These foods include kidney beans, lentils, grapefruit, skim milk, peas and peanuts, as well as raw apples and carrots. Sweet potatoes just make it into this category, with a glycemic index of 54. The "medium" category includes foods with a glycemic index of 56 to 69. Raisins, pineapple, sweet corn and bananas fall into this category, as well as ice cream with a glycemic index of 61. All foods that have a ranking of 70 to 100 are classified as having a high glycemic index. White bread has a glycemic index of 70, baked potatoes have an index of 93, and instant white rice, watermelon and brown rice also have a high glycemic index.
Considerations
The real flaws in the glycemic index typically relate to high-fat foods, which are digested more slowly than low-fat foods. For example, candy bars actually register a low glycemic index, but this is likely due to their high fat content. Because the glycemic index doesn't measure the actual nutrient content or "healthiness" of foods, many low glycemic index foods are often less healthy than some high-index foods, according to MayoClinic.com. This can become confusing for dieters and even dangerous for some people, because numerous low glycemic-index foods contain lots of saturated fat, calories and even sugars.
