I.M.120 Helping you to BE YOUR BEST SELF

Developed around 1980 by Dr. David Jenkins of Toronto, the glycemic index was originally designed as a way to determine the effect of an individual food on blood sugar levels. The focus was on diabetics. This theory was that if the rate of blood sugar increase after a meal was slower, their impaired ability to manage blood sugar would be improved.

This is known as postprandial blood sugar. The blood sugar that occurs after food is ingested and that food is absorbed into the bloodstream.

The Effect of Blood Sugar on Insulin

As the sugar goes off after a meal, the body must produce more insulin in order to properly manage the higher sugar levels. Think of insulin as a hormone that grows fat cells. The more insulin in the bloodstream, the more the tendency for fat cells to grow.

A good comparison is to growth hormone. At the time of our youthful growth spurt, our vertical growth is stimulated by growth hormone. We do not grow taller because we eat more, we eat more because we are stimulated by growth hormone. In a similar fashion, insulin drives fat growth. The more insulin we have, the more our fat cells are stimulated to grow.

Researchers and clinicians interested in controlling obesity have taken the data on glycemic index and applied it to the obesity model of care.  The theory is that if we can lower the level of insulin a person excretes over the course of the day, they will make less fat.

Thus the glycemic index.  The food with the highest glycemic index is sugar. It is given the value of 100 for the purpose of rating all other foods.  The higher the glycemic index of a food, the more quickly and efficiently it gets into the bloodstream as sugar and the more vigorously it will stimulate insulin production. 

 More insulin, more fat, more hunger, more need for food, and so the cycle goes.

While the glycemic index can be a useful guide in food selection, it has never been shown to be profoundly effective when used by itself as a weight-loss tool.

This may be due to a factor known as glycemic load.  While the glycemic index is a reflection of the power of a given amount an individual food will raise sugar and insulin levels, it does not account for the volume of food eaten.

A person can eat a very low glycemic diet, but have a high glycemic load and still gain weight.

Many times I've had patients say to me that they are frustrated by their inability to lose weight. They cite the fact that they only eat healthy food.  I do believe them, however what they may be failing to recognize is that even healthy foods taken in amounts beyond the body's needs will lead to fat production.

Foods that have an especially high glycemic index, and also a high  glycemic load are some of the following; refined flowers such as bread and cereals, liquid carbohydrates including juice and beer, starches including potato, rice, and corn.

The use of bread in our diet can be an especially vexing problem for people stuck in a cycle of obesity. Even multigrain and whole wheat breads are very fattening.

Sugar and high fructose corn syrup are in the class by themselves with regard to stimulation of obesity.

High fructose corn syrup probably stands all alone in it's uniquely fat stimulating effects. First introduced in 1978, as the name implies this substance has a large amount of fructose combined with glucose. This combination makes it very efficient at creating fat.  Fructose is metabolized in the liver where it is converted to fat for storage. Glucose creates an immediate spike in blood sugar driving up insulin.

It may not be entirely coincidental that America's obesity epidemic seems to coincide with the introduction of artificial foods such as high fructose corn syrup.

Fruits represent a special circumstance for people trying to lose weight. While generally regarded as safe and healthy, modern fruits have been genetically engineered to be especially succulent. This usually means increasing the fructose amount in the fruit. As mentioned above, fructose is uniquely obese inducing.

There are some things you can do to alter the glycemic index of the food you eat. One is to increase the amount of fiber at the time of eating. This tends to reduce the absorption of foods there by altering their glycemic index.

Vinegar can also reduce the glycemic index of food you eat. Then again, if you put enough vinegar on your food, you're likely to make it taste so bad that you want to eat it in the first place.

The ingestion of wine at the start of a meal can also increase the glycemic index. Consult with your doctor regarding safe limits, but a generally accepted amount is up to three glasses for men and up to two glasses for women.

We use the glycemic index as a guide in food selection. As a stand-alone intervention, it will not help you achieve your goal of significant weight loss.  However, when coupled with other strategies including nutritional and behavioral change and in most cases careful use of supplements and medications, it can be a critical component of the permanent change in eating patterns required to achieve and maintain your healthiest weight.

-Dr. Stephen Petteruti