Nutritional scientists from the University of Toronto introduced the glycemic index in 1981. They were looking for a way to help diabetics control their blood sugar levels through diet. Other nutritionists took notice of the program's success and began promoting glycemic index diets as a way to control appetite, promote weight loss and improve athletic performance, according to the G.I. Handbook.
Function
GI diets help dieters, diabetics and other people concerned with blood sugar stability to choose healthy carbohydrates. Under the glycemic index, a healthy carbohydrate is one that causes blood sugar to rise and fall slowly and steadily. These foods are said to have a low glycemic index. Foods with a high glycemic index cause a steep rise and fall in blood sugar, which provides a quick burst of energy followed by a crash. High glycemic foods may leave you feeling hungry again soon after you eat. This may cause you to consume more calories than you need, which may cause weight gain and other health problems, according to the G.I. Handbook.
Identification
To identify the glycemic index rating for a particular food, you will need to consult a glycemic index table, available online through sources such as the American Journal of Clinical Nutrition. The glycemic index rates foods on a scale from 0 to 100. Healthiest choices include foods rated 55 or lower. Factors that reduce the GI rating for a food include protein, fat, fiber and acid content, according to the Harvard School for Public Health. Processing, milling and grinding increase the GI rating for a food.
Staples
Beans, most vegetables, whole wheat pasta, whole grains, nuts, lean protein and fresh fruit form the foundation of glycemic diets, according to the Harvard School for Public Health. Foods to avoid include cookies, cake, candy, white flour, snack chips, white potatoes and most root vegetables.
Benefits
Following a low glycemic diet helps you to maintain stable blood sugar levels, which may help you better control your appetite and how much you eat, according to the G.I. Handbook. Stable blood sugar will also help you sustain energy levels throughout the day or through the duration of an athletic activity. Consuming a diet based on high glycemic foods appears to increase risk for diabetes, heart disease and obesity, according to the Harvard School for Public Health.
Tips
Do not confuse glycemic index with glycemic load, a revised rating system that takes into consideration the amount of digestible carbohydrate in the food. Under this advanced rating system, a glycemic load of 20 or more is high, according to the Harvard School for Public Health. Under the GI rating system, a food is not high until it reaches a rating of 70 or higher; 55 to 70 is considered moderate. Most tables provide information for both glycemic index and glycemic load. The GL analysis of carbohydrates may be a more precise guide to healthy carbohydrates, according to the Calorie Control Council.
Considerations
The glycemic index is not enough to help you make good food choices, according to the Harvard School for Public Health. A Snickers bar, for example, has a moderately low GI rating of 41 due to its fat and protein content. This does not, however, make it a healthy choice; a Snickers bar provides mostly empty calories.
References
- "The G.I. Handbook: How the Glycemic Index Works"; Barbara Ravage; 2005
- Harvard School for Public Health: Carbohydrates and the Glycemic Index
- Glycemic Index Foundation: What is the Glycemic Index?
- Calorie Control Council: Glycemic Index
