If you've been trying to lose weight -- whether for health reasons or simply to fit back into your skinny jeans -- you've most likely heard of the glycemic index, a system used by people on a low-carb diet to help them keep track of how the foods they eat affect their blood sugar levels.
In 1981, Dr. David Jenkins and his colleagues at the University of Toronto created the glycemic index as a way of ranking carbohydrates based on how they affect blood sugar levels.
The index is used primarily to test the relationship between diet and the prevention and treatment of chronic conditions such as heart disease, cancer and diabetes.
Good Carbs v. Bad
Simply put, the glycemic index ranks good carbs vs. bad carbs.
Carbohydrates that break down quickly during digestion have the highest glycemic indices. Those that break down slowly, releasing sugar gradually into the blood stream, have a low glycemic index.
The higher the glycemic index, the faster your body will process a food and the sooner you'll be reaching for the cookie jar to satisfy your cravings.
It's no surprise, especially to those familiar with low-carb diets, that high glycemic index foods include those made from refined flour, such as bread, pasta and rice -- the very things forbidden on low-carb diets. The body processes these foods so quickly that blood sugar spikes soon after you eat them.
But the sugar high is followed by a crash a short time later, leaving you with a bad case of the munchies. Unfortunately, your craving will most likely be for more of the same processed food that led to the crash.
In contrast, low glycemic index foods, such as fruits, vegetables and whole grains, release energy more slowly. This gradual rise in blood sugar levels provides long-term energy and keeps cravings at bay.
In general, foods with a ranking of 55 or less on the glycemic index are considered to be low glycemic. Medium glycemic index levels are between 56 and 69. You should try to avoid foods with a glycemic index over 70.
Lists of low, medium, and high glycemic index foods are available online, with a searchable database at
GlycemicIndex.com.
System Has Limitations
In general, unprocessed foods tend to have lower glycemic indices than refined foods. But the system has its limitations.
Dr. Shari Lieberman, author of Transitions Lifestyle System Glycemic Index Food Guide, said that because a food has a low glycemic index does not necessarily mean it's healthy.
For example, GlycemicIndex.com gives chocolate cake a low glycemic index ranking of 38. On the other hand, pineapple, a fruit you think would rank low on the scale, boasts a glycemic index of 66.
But don't assume that you can have your cake and eat it too. A food's glycemic index is influenced by several factors. These include the other foods eaten at the same time, the protein-to-fat ratio of a meal, how the food is prepared, the time of day you consmue it and your level of activity or exercise around the time of a meal.
Remember that eating low glycemic foods alone won't make you lose weight. It's the effect these foods have on your blood sugar levels that may eventually help you shed fat, researchers say.
But before you jump on the glycemic index bandwagon, be aware that, like any diet, the reality is often much different than the claims. No single diet will help everyone lose weight.
Furthermore, a U.S. Dept. of Agriculture-Tufts University study concluded that if you're trying to lose weight, calories count more than the type of foods you eat. The study also showed that after one year, overweight people on a low-carb, low glycemic index diet lost just as much weight as people on a reduced fat, high glycemic diet.
In the end, diet success depends on what works best for you over a long period of time. Aim not for short-term weight loss, doctors say, but for dietary changes that will last a lifetime. Using the glycemic index ranking of foods is just one of the tools that can help you accomplish this.
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