Glycemic Index and Glycemic Load: Know the Difference



By Amber Alexander

Amber Alexander

Much of dieting focus recently has been placed on the glycemic index. While understanding and managing the glycemic index is important, it's equally important to go one step further and understand glycemic load. The glycemic load is a relatively new way to measure the impact of food to blood glucose levels. Simply put, glycemic index represents glucose conversion speed, while glycemic load represents the amount of glucose created.

So What's the Glycemic Index?

The glycemic index is the relative degree to which blood sugar increases after the consumption of food, that is, relative to the effect of pure sugar. High glycemic index foods can raise blood glucose levels very quickly, as well as insulin levels. In contrast, low glycemic index foods don't significantly raise blood glucose levels and insulin levels after eating. Pure glucose is given a value of 100 while other foods are given an index number representing its relative effect on blood glucose levels.

For example, sweet corn has an index number of 55 meaning it raises blood glucose levels 55 percent as much as pure glucose. Generally, foods below 55 are considered low glycemic index foods, 55-70 represents mid-glycemic index foods and over 70 are considered high glycemic foods. Previous belief was that simple sugars dramatically increased blood glucose levels while starches such as potatoes and bread were digested slowly. The results from numerous studies, however, show this is not the case. Potatoes, for example, reported an average index of 84, making it one of the higher glycemic foods available.

So highly glycemic foods drive an insulin spike, followed by an insulin crash. This yields a surge of energy when the insulin converts the carbohydrate into glucose, and then an energy crash when it's used up. But here's what's worse: the glucose that floods our system from highly glycemic carbohydrates, if not burned up, is converted to fat. The body has no other use for it.

Get the picture? Highly glycemic foods equals bad news for anyone looking to lose fat.

This is the same thing as simple carbohydrates v. complex carbohydrates; simple carbohydrates are highly glaucemic (breaking them down into glucose is a simple process), while complex carbohydrates take more time (breaking them down into glucose is a complex process). The result from complex carbohydrates, or low glycemic foods, is a steady low dose of glucose while actually using more energy (calories) for digestion.

Knowing Glycemic Load

It's important to know that, although important, the glycemic index only tells part of the story, because while it tells us how quickly a specific carbohydrate is converted to glucose, it doesn't tell us how much glucose it will contribute. That's where the glycemic load comes in.

Take watermelon, for example. Watermelon has a high glycemic index of 72, bad right?  Not really, because watermelon doesn't have all that much sugar in it, so its glycemic load is a relatively low 4. A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low.
We get the glycemic load by taking the glycemic index x 100 x the total carbohydrate available in grams. Below is a chart showing both GI and GL ranges.

Source: mendosa.com

So when discussing the glycemic index, be sure to include reference to the glycemic load which tells the complete story on what a carbohydrate does to our blood glucose levels, and ultimately to our body fat.

For a comprehensive, printable list of GI an GL values (yes, print this and tape it to your refrigerator), click here and scroll down.

Amber is a figure competitor, fitness instructor, fitness model and a candidate for Bodybuilding.com's BodySpace spokes model, her username is Amber3478. Vote for Amber at the BodySpace spokes model contest site now!