The glycemic index, or GI, diet was originally developed as a tool to help diabetics control their blood sugar, although it has evolved into a weight loss plan. The GI diet involves a ranking of carbohydrates, called the glycemic scale, based on the effect that the carbohydrates have on your blood glucose level. Proponents of the GI diet believe that choosing carbohydrates with a low GI can help control blood sugar as well as promote weight loss.
Physiology
Your body breaks down different types of carbohydrates at different rates. Some carbohydrates move through your digestive system quickly, causing rapid increases in blood glucose levels, which also signal your body to release significant amounts of insulin. Insulin attaches to glucose and brings it to your tissues, which brings your blood glucose back to normal. The higher your blood sugar, the more insulin you need to control it. Other carbohydrates move through your digestive system at a slower pace. These carbohydrates still increase your blood glucose and trigger the release of insulin, although to a lesser extent.
Theory
The theory behind the GI diet is that when your blood sugar and insulin levels stay high for an extended period of time or they fluctuate up and down repeatedly, your cells become less sensitive to the effects of insulin. As a result, your pancreas must produce more insulin to have the same effect. Over time, your tissues can become completely desensitized, leading to a condition called insulin resistance, which is associated with obesity, type 2 diabetes, high blood pressure, stroke and heart disease.
Glycemic Scale
According to EveryDiet.org, pure glucose has a glycemic ranking of 100. This is because glucose is the most rapidly moving carbohydrate. Other carbohydrates are ranked based on the glycemic index of glucose. Foods with a glycemic index between 70 and 100, such as potatoes and white bread, are classified as high glycemic foods and you should avoid them on a glycemic index diet. Foods between 56 and 69, such as bananas and corn, are classified as medium glycemic index and you should consume them sparingly. Most of your carbohydrate intake should be in the form of low glycemic foods, such as apples and beans, which are given a rank of 55 or lower.
Considerations
Some critics of the diet claim that the glycemic index diet is not entirely accurate because it only ranks foods based on their individual effect on your body. The diet does not take into consideration the fact that foods may react differently in your digestive system when eaten with different types of foods or in different amounts. Since most people do not eat only one type of food at a time, this is an important factor to consider.
References
- EveryDiet.org; Low Glycemic Index Diets; March 24, 2011
- MayoClinic.com; Glycemic Index Diet; November 24, 2009
- "Nutrition and You"; Joan Salge Blake; 2008
