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Glycemic Index 101

If you’ve been to NUTRI-BODIES and inquired about calorie consumption, then you’ve probably listened to a quick speech about the Glycemic Index. Whether for fitness or general health, the GI should be a major consideration in meal planning.

Carbohydrates (a.k.a. “carbs”) – A few bad seeds ruined it for all

Around early 2000, carbohydrates took a major backseat as the protein-diet craze rocketed on to the scene. Weight watchers were tossing out all their carbohydrates in favor of bacon, barbeque ribs, hamburger meat and any other protein source they could get their hands on. While some lost a few pounds they also acquired many health problems in the process from consuming high levels of saturated fat and cholesterol.

Why all the hostility toward carbs? Simple, the westernized diet contains a lot of empty calories primarily from carbs. Who would’ve thought the all-you-can-eat pasta buffets, late night super-sized taco binging, and chocolate bars were helping to make our nation obese? These bad carb choices along with ill portion sizes and late-night meal timing have grouped carbohydrates in an unpopular food category. This is criminal.

Enter the Glycemic Index (GI)

Many of you know that carbs are not created equal and that there are “good” and “bad” carb choices. We primarily know this because of the great people responsible for extensively testing carbohydrates from foods and helping us make better carb choices. This information is translated to a special food index known as the glycemic index (GI).

The GI was introduced in the American Journal of Clinical Nutrition in 1981 by David J.A. Jenkins, M.D., Ph.D., D.Sc, and colleagues1. As of this blog, Jenkins is the University Professor and Canada Research Chair in Nutrition and Metabolism for the Department of Nutritional Sciences. Jenkins and colleagues researched 62 foods and sugars. Now thanks to continual efforts by Professor Jennie Brand-Miller of the University of Sydney’s Human Nutrition Unit, School of Molecular and Microbial Biosciences and the University’s GI Group, more than 2500 foods and sugars now have GI values. Finding great tasting healthy carbohydrates to consume has never been easier!

What is the GI

The glycemic index (GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the extent to which they raise blood sugar levels after eating. Foods with a high GI are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health. Low GI diets have been shown to improve both glucose and lipid levels in people with diabetes (type 1 and type 2). They have benefits for weight control because they help control appetite and delay hunger. Low GI diets also reduce insulin levels and insulin resistance2.

Glycemic Load (GL)

While the GI is a great indication of what foods you should choose to eat, the glycemic load (GL) also factors in the quantity of food. As you consume a carbohydrate your blood glucose (blood sugar) levels will rise and fall. How high your blood glucose rises and for how long is represented by the GL. GL is a combination of both GI (quality of the carb) and the quantity of carbohydrate in your food.

GL is the combination of the food’s GI multiplied (X) by the amount of carbohydrate of the serving and finally divided by the number “100”: GL = (GI x the amount of carbohydrate) divided by 100.


A medium single apple has a GI of 40 and it contains 15 grams of carbohydrate.
GL = 40 × 15/100 = 6 g

A white bread bagel (70 grams) has a GI of 69 and it contains 35 grams of carbohydrate.
GL = 69 × 35/100 = 24 g

In this case we see that the white bread bagel is a poor choice due to its higher GI and GL (4x) compared to the apple. Ultimately the GI experts recommend using the Glycemic Index when choosing which foods to eat, but you should also keep an eye on the serving size and ensure you are eating proper portions.

Where to find the GI Index

The official website of the glycemic index and GI database is located online at www.glycemicindex.com. You can use their extensive database to find virtually all types of carbs to help with your meal planning. Also visit their blog at www.ginews.blogspot.com which is loaded with all sorts of great GI related content including low-GI recipes.

Need something a little more portable? You’re in luck because many books have been published about the GI: www.glycemicindex.com/books.htm.


1 DJ Jenkins, TM Wolever, RH Taylor, H Barker, H Fielden, JM Baldwin, AC Bowling, HC Newman, AL Jenkins and DV Goff. Glycemic index of foods: a physiological basis for carbohydrate exchange. American Journal of Clinical Nutrition. 1981 Vol 34, 362-366.

2 Jennie Brand-Miller. About glycemic index. Human Nutrition Unit, School of Molecular and Microbial Biosciences, University of Sydney. 2009 http://www.glycemicindex.com/aboutGI.htm.

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Written on October 14, 2009 by Brian Putchio
Last Updated: July 06, 2010

This information is not intended to take the place of medical advice.Please check with your health care providers prior to starting any new dietary or exercise program. CasePerformance is not responsible for the outcome of any decision made based off the information presented in this article.

About the Author: Brian Putchio is owner/operator of NUTRI-BODIES, LLC in Dubuque, Iowa. Through his extensive knowledge and experience in the nutraceuticals industry since 1999, Brian offers a unique perspective to his blog readers. Brian's refusal to simply flow with the marketing strategies of the industry conveys a strong sense of credibility that helps consumers successfully navigate the nutraceutical minefield.