South Beach Diet Guide:

The Glycemic Index Explained

One of the keys to the South Beach diet is the concept of a "Glycemic Index".

The "Glycemic Index" concept was originally developed a team of scientists lead by Dr. David Jenkins at the University of Toronto in 1981; it is now gaining widespread acceptance as part of a dietary strategy.

It was written about back in 1989 in Michel Montignac's book, "Dine Out and Lose Weight", and has since spawned several variants ("Sugar Busters", "The G.I. Factor", "The New Glucose Revolution", "The G-Index Diet" ... the list goes on).

The Glycemic Index of a food is the measure of the rise in the level of glucose that occurs in your bloodstream, after that food is ingested.

When you eat foods with a high glycemic index, your blood sugar levels shoot through the roof.

This causes your pancreas to secrete insulin, which is your body's way of getting your blood sugar level back to normal.

However, the secretion of this insulin:

  • causes our bodies to store excess sugar as fat,
  • inhibits the "burning" of previously stored fat, and
  • signals our liver to make cholesterol!

Furthermore, as foods with a low glycemic index ("G.I.") are absorbed more slowly, the calories from the food you eat are more likely to be burned throughout the day as energy, rather than stored as fat.

In fact, studies have shown that even when calorie intake is the same, you can lose more weight eating low G.I. foods rather than high G.I. foods.

The Glycemic Index of a food is derived by comparing the rate of digestion to that that food, with the rate of digestion of pure glucose. Glucose* is assigned a Glycemic Index of 100, and the tested food is charted against this standard.

* glucose if the most widely accepted reference food, however some other systems use white bread instead.

Foods with a high Glycemic Index (70 and above) are those that break down quickly and cause a spike in blood sugar levels.

Foods with a low Glycemic Index (55 and below) break down more slowly and steadily, resulting a more sustained supply of energy.

Popular notions regarding the rates of absorption of "simple" and "complex" carbohydrates (as was thought to be the case in the 1970's) are refuted by a glance at the Glycemic Index tables.

Foods high in sugar - such as chocolate, candy and ice cream was classed as "simple carbohydrates".

For years, we thought these foods were quickly digested, leading to a rapid rise in blood sugar.

Similarly, it was believed that starchier foods like bread and potatoes ("complex carbohydrates") broke down more slowly, providing steady, long-term energy.

However, in 1981, Dr. David Jenkins found this was not necessarily true. Dr. Jenkins, a professor of nutrition at the University of Toronto, set out to establish the type of foods that were best for people suffering from diabetes.

Jenkins found that foods such as potatoes — traditionally defined as a complex carbohydrate — actually led to a rapid rise in blood sugar. Some foods high in simple carbohydrates appeared to digest more slowly, leading to a gradual elevation in blood sugar.

This led researchers to classify foods according to their glycemic index. The glycemic index refers to the immediate rise in blood sugar that occurs after you eat a food high in carbohydrate.

• Foods that digest rapidly lead to a fast release of glucose into your blood stream. These are known as high glycemic index foods.

• Foods that digest more slowly release glucose into your blood gradually, and are known as low glycemic index foods.

.Next: Glycemic Index Charts

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The "South Beach Diet Guide" is a free information source about the SouthBeach Diet.
This site is not ensorsed by or associated with Dr. Agatston or his publishers, nor is it intended as medical advice.