Diets that use the glycemic index claim that controlling blood sugar is the key to weight loss. The glycemic index, or GI, measures how quickly food raises blood sugar; foods are ranked from 1 to 100 in comparison to pure glucose -- which scores 100. The higher a food scores on the GI, the faster your blood sugar will rise and the more insulin your body will produce.
Low-GI Diet Basics
Many popular diets are based on the GI, including the Zone, Sugar Busters and Nutrisystem. Foods that score less than 55 on the glycemic index are considered low-GI foods. Medium-GI foods score between 55 and 69 and high-GI foods score over 70. The GI can only rank foods that contain carbohydrates -- only carbohydrates raise your blood sugar level. Eating carbohydrates with other foods that slow digestion, such as fiber, fat or protein, can lower the GI score of your meal and keep blood sugar stable. Foods low on the glycemic index aren't always healthy -- high fat foods such as chocolate can score well, sometimes even lower than fruit. The GI can be a guide, but you'll still need to choose nutrient-dense foods.
GI, Fiber and Weight Loss
One of the reasons for the success of low-Gi diets is the high fiber content in many low-GI carbs. Fiber is only found in plant foods, and it can't be digested by your body -- so it doesn't add to your total caloric intake. In addition, fiber slows digestion. According to MayoClinic.com, "because low glycemic index foods are absorbed more slowly, they stay in your digestive tract longer. This may help control appetite and delay hunger cues, which can help with weight management." The Joslin Diabetes Center notes that foods high in soluble fiber, such as oatmeal, may also help stabilize glucose levels.
The GI and Other Health Concerns
According to Australia's University of Sydney Glycemic Index Research Center, following a low-GI diet can improve both blood sugar and cholesterol levels and can help prevent obesity, diabetes and coronary artery disease. A 2009 study from the "Journal of the American Dietetic Association" showed that a low-GI diet can prevent hypoglycemia -- or high glucose levels -- in people with Type 2 diabetes.
MayoClinic.com points out that almost any diet that promotes healthy weight loss can lower your risk for diabetes, high cholesterol and heart disease.
What to Eat on a Low-GI Diet
Following a low-GI diet means choosing foods that aren't just low on the glycemic index, but that also have essential vitamins and minerals your body needs. Almost all vegetables and most fruits are low-GI. Exceptions include starchy vegetables such as potatoes and corn, and high-sugar fruits such as pineapple, watermelon and bananas. Dried fruits, because they have concentrated amounts of sugar, are also higher on the GI. Because of their high fiber content, whole grains and brown rice are lower on the GI than refined grains and white rice. You'll still need to practice portion control -- just because foods are low on the glycemic index doesn't mean they are low-calorie or low-fat.
References
- MayoClinic.com: Glycemic Index Diet - Losing Weight with Blood Sugar Control; November 24, 2009
- Glycemic Index: About the Glycemic Index
- "Journal of the American Dietetic Association"; The Effect of a Low-Glycemic Diet Vs a Standard Diet on Blood Glucose Levels and Macronutrient Intake in Children with Type 1 Diabetes; AJ Rovner; February 2009
- Joslin Diabetes Center: How Does Fiber Affect Blood Glucose Levels?
