By: Mauro Di Pasquale

[ Q ] What is the Glycemic Index (GI)?

It is simply a measure of how much a food will contribute to a person's blood sugar level. The higher the index of a food item, the more rapid the increase in blood sugar level is. 'Sweet' food like maple syrup, chocolate, ice cream and 'starchy' food like potatoes and donuts are rated high in glycemic index.

In contrast, food high in fiber like whole-grain rye bread and All-Bran cereal are rated low in glycemic index.

[ Q ] How is the GI determined?

Glycemic index is assessed by having one or more people eat a specific amount of a single food (usually 50 grams of digestible carbohydrate [total carbohydrate minus fiber]) and then measuring the change in blood sugar levels compared to the levels achieved after they have eaten a control food such as white bread.

The average change in blood sugar levels over a set period of time relative to the levels after consumption of the control food is the food's glycemic index.

[ Q ] What is Glycemic Load (GL)?

Low GI foods that are high in carbs may be as troublesome as higher GI foods that contain only a small percentage of carbs, if eaten in large amounts. This is why glycemic load (GL) is important. It ranks foods according to actual carb content (eg. in a typical portion-size), not how fast a 50g amount of carbs raises blood sugar levels.

Harvard School of Public Health professorand researcher Walter Willett, M.D., and his associates developed this concept as long ago as 1997, when they published journal articles on the subject.

But it was only in their Harvard Women's Health Watch article and Dr. Willett's new book that they have published many of the GL numbers.

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[ Q ] How is Glycemic Load (GL) Calculated?

Glycemic load tells you how much carbohydrate is in the food, rather than just how high or how rapidly it raises blood sugar levels. To calculate glycemic load in a typical serving of food, divide the GI of that food by 100 and multiply this by the useable carbohydrate content (in grams) in the serving size.

[ Q ] Can you give an example of GL Calculation?

Take carrots for example, according to some GI tests, carrots have a glycemic index of 49. They contain about 7 grams of carbohydrate per 100g of carrots. So to calculate the glycemic load for a standard 2oz (about 50g) serving of carrots, divide 49 by 100 (0.49) and multiply by 3.5.

The glycemic load (GL) of carrots is therefore 1.7. In some GI tests, carrots score as high as 95 for glycemic index. Even so, the glycemic load for a 50g serving size of carrots is still only 3.3.

[ Q ] How Does Glycemic Index or Glycemic Load Affect Hunger & Obesity?

High glycemic diets can cause excessive calorie-intake and obesity. For example, if we eat a high glycemic food or a high glycemic load meal, which by definition triggers a rapid rise in our blood sugar levels, our pancreas is over-stimulated and releases a much larger amount of insulin.

Result? This large quantity of insulin rapidly mops up the excess sugar in our bloodstream causing our blood sugar levels to dip quickly below normal, causing us to feel hungry once more.

So even though we may have eaten a high calorie meal, we are induced to feel hungry and eat again within a comparitively short time. This process may lead to excessive calorie intake and weight gain, possibly causing obesity.

[ Q ] How does GI and GL related to low-carb diet like Metabolic Diet?

GI and GL are actually the basis for diets like Metabolic Diet and is the ranking of foods based on the way they increase a person's blood glucose level. A rise in blood glucose (or sugar) levels causes a rise in blood insulin levels.

Low carb diets work on the premise that the rise in blood insulin levels cause increased weight gain by telling your body to store fat.

In addition, the rapid rise in blood insulin levels causes a rapid fall, which causes hunger and, even though your body may not need calories for energy, this causes you to eat (or overeat) which starts the cycle all over again!

Low Carb Diets: The Way To Go? Hopefully by the end of this article you will have a more rounded view on carbohydrates and if you still want to follow the low carb route for fat loss I should be able to show you a plan that will at least negate some of the negative elements of low carb diets! [ Click here to learn more. ]

[ Q ] Are there Other Important Diet Considerations?

GI should not be your only criterion when selecting what to eat. The total amount of carbohydrate, the amount and type of fat, and the fiber and salt content are also important dietary considerations.

The glycemic index is most useful when deciding which high-carbohydrate foods to eat. But don't let the glycemic index lull you into eating more carbohydrates than your body can handle, particularly if you have diabetes.

[ Q ] How useful is Glycemic Load as a health indicator?

It is useful in determining risks to certain types of cancer. A large national Women's Health Study shows that women with the highest glycemic load are nearly three times as likely to develop colorectal cancer in the next eight years than those with the lowest glycemic load. In an earlier study, men and women with the highest glycemic load were 80 percent more likely to develop colon cancer compared to those with the lowest load.

A high glycemic load may also raise the risk of uterine and stomach cancer by 24 to more than 100 percent, compared to those with lower glycemic loads. Researchers think that diets that repeatedly raise blood sugar levels cause insulin levels to soar. Insulin and insulin-related growth factors, in turn, appear to promote the development of some cancers.

[ Q ] Where can I get a comprehensive list of GI and GL of food items?

A good resource is this link: http://www.bodybuilding.com/fun/gifoods.htm.

Sources

http://www.dietitian.com/carbos.html
http://www.ific.org/publications/qa/glycemicqa.cfm
http://www.diet-i.com/glycemic-index-diets-obesity.htm
http://diabetes.about.com/library/mendosagi/nmendosagi.htm
http://www.msnbc.msn.com/id/5016119

mauro@metabolicdiet.com

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