Before the glycemic index came around in the early 1980's, carbohydrates were traditionally known as either simple or complex. Simple carbohydrates are quickly absorbed from the intestine into the bloodstream, causing a sharp rise in blood sugar. Examples of simple carbohydrates include soft drinks, desserts, doughnuts, white bread, pancakes and other white-flour products.

Complex carbohydrates are slowly absorbed from the intestine into the bloodstream, causing a more gradual and moderate increase in blood sugar. Examples of complex carbohydrates include oatmeal, whole grains, legumes such as kidney, pinto and navy beans along with other vegetables like asparagus, beans, broccoli and peas.

The glycemic index provides a more accurate look of carbohydrates and their effect on blood sugar levels. The glycemic index ranks carbohydrates on a scale from 0 to 100 according to how much they raise blood sugar levels after eating. Carbohydrates that breakdown quickly during digestion are higher on the glycemic index because the blood glucose response is fast and high.

Carbohydrates that break down slowly, releasing glucose gradually into the blood stream, naturally rank lower. If you are like me, you might be wondering right about now just how this glycemic index has anything at all to do with fat loss or muscle building. But do not let these technical terms throw you because blood sugar is very important to your fitness goals and overall health!

Two fitness experts weigh in on their opinion of using the glycemic index as a weight loss tool. They believe that while it may be useful to a degree, it has its flaws and shouldn't be relied on entirely to reach your fitness goals. Here are their articles:

Weighing in on Your Food by Jon Benson and, The Glycemic Index: What You Need to Know by Christian Finn

Downing large quantities of carbs high on the glycemic index causes a rapid increase in blood sugar levels. This rapid rise in blood sugar is followed by a rapid fall because of the insulin that is released to get your blood sugar levels back to normal. When this rapid fall occurs, your appetite will spin out of control and you will likely go on an eating frenzy. The result is you will take in more calories during the day than you burn, which leads to those excess calories being stored as fat.

To demonstrate this, try this as a test - eat a bagel or a few pieces of white bread for breakfast and nothing else and make sure that you don’t leave the table until you are full. I can almost guarantee you that you will be starving long before its time for lunch.

Research has shown that by eating carbohydrates that make your blood sugar rise and fall quickly, you will eat more calories at your next meal. It's very important to try to maintain steady blood sugar levels to prevent feeding binges and the excess calories that come with them.

"Crash-and-burn eating" can also cause fatigue, burnout and destroy your workouts. When your blood sugar is constantly rising and falling abruptly (from eating mostly high glycemic carbohydrates), your adrenal glands respond by releasing lots of adrenaline and stress hormones. This makes you tired, worn-out and feeling like you have just worked a double! Workouts become all but meaningless when your blood sugar crashes because you have no energy. A stable blood sugar level during exercise increases workout output and prolongs the time you can exercise before getting exhausted.

Now do you want to hear something truly depressing? Those same high blood sugar levels that kill your workouts will also make you look older. Research on aging has found that increased blood sugar levels (caused by eating carbs high on the glycemic index) hastens the aging process!

Finally, low blood sugar levels can cause profound fatigue. Try eating a bagel right before a meeting or lecture and see how alert you are about half way through. You'll know when your blood sugar crashes because you'll get very tired, fairly quickly.

There are times when consuming high glycemic carbohydrates can work to your advantage especially during a short-duration workout (less than 60 minutes) and immediately after a workout. The rapid rise in blood sugar levels brought about by high glycemic carbohydrates provide "quick fuel" during workouts and restore glycogen levels in muscle after a workout. To read more about the importance of consuming carbohydrates high on the glycemic index after a workout, read the article titled, Window of Opportunity.

Balance is the key to success, both in life and in your body. The body functions best with steady, but moderate, blood sugar levels. This is possible by eating slow-burning carbohydrates, which are foods low on the glycemic index. By eating more of these, you will maintain a steady, healthy blood sugar level that will give you a constant level of mental and physical energy. Plus, you can cut down on cravings and hunger by eating foods that are on the lower-end of the glycemic index.

When you do eat high glycemic carbohydrates, then be sure to balance them with low glycemic carbohydrates. For example, eating foods high in fiber alongside foods high on the glycemic index will slow the absorption of sugar into the blood from the intestine. Of course, staying in shape never hurts either. Reseearch shows that physically fit men are less likely to have big swings in their blood sugar levels so they can tolerate foods high on the glycemic index better than those that aren't physically fit. Fit men also make less insulin when they eat high glycemic carbohydrates than unfit men.

Now that you have a basic understanding of blood sugar and its impact on your fat and muscle-building goals, here's a partial glycemic index chart to reference. For access to an entire glycemic index database, click here.

Glycemic Index Range:
Low GI = 55 or less
Medium GI = 56 - 69
High GI = 70 or more

Glycemic Index of Common Foods