The Glycemic Index

The Glycemic Index

by Valerie Kirk

Low is good.  High is bad.  But what exactly is the glycemic index? The glycemic index is a scale that assigns a number to every food. It is used to indicate how fast and how high a particular food can raise our blood glucose (blood sugar) level. 



The higher a food's glycemic index number, the faster our blood sugar levels will tend to rise after we eat it. Why is this bad? Sugary foods, such as candy and soda (ranked high on the GI), make your blood sugar rise quickly to a high point. That blood sugar level won't stay high for long, though, and you'll experience a "crash" feeling when it drops again.

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Low-glycemic foods raise your blood sugar slowly and moderately, helping to keep your blood sugar more stable so you won't get that crash. Making yourself aware of what glycemic index the food your eating has can help you control your blood sugar levels, and possibly prevent heart disease, certain cancers, improve cholesterol levels, and achieve or maintain a healthy weight. Here’s a more detailed look at the Glycemic Index (GI):

What types of food does the glycemic index apply to?

The glycemic index applies to carbs only, as protein and fat have little affect on blood sugar levels. Starchy foods tend to have a high glycemic index and can raise blood sugar levels notably after meals.

Where did the idea of the glycemic index come from?

The concept was developed by Dr. David J. Jenkins and colleagues in 1980–1981 at the University of Toronto in their research to find out which foods were best to help control blood sugar in people with diabetes. The blood sugar spikes of high-GI foods can be particularly troublesome for diabetes sufferers because these individuals have difficulty regulating blood sugar.

Which foods are high on the glycemic index?

Foods like potatoes, rice, and white bread are examples of high glycemic foods. The majority of non-starchy fruits and vegetables are low glycemic foods and may help prevent high blood sugar after consumption.

Low glycemic index: 55 or less (broccoli, lettuce, red peppers, cherries, apples, oranges, eggs, meat)
Medium glycemic index: 56-70 (fresh corn, beets, apricots, cantaloupe, pineapple, whole wheat products)
High glycemic index: 70 or more (pumpkin, watermelon, white rice, white bread, cereals, processed foods)

Can the glycemic index help me lose weight?

The glycemic index has gained popularity as a dieting tool thanks to the hype that eating low-GI foods can curb appetite and help individuals lose weight. On Atkins, South Beach, and Nutrisystem, dieters are urged to select carbohydrate foods low on the glycemic index. These foods tend to be more nutritious, less refined, higher in fiber, and lower in calories than their high-GI counterparts. Low-GI foods are also broken down more slowly, allowing individuals to feel full longer and curb overeating. To lose weight using the glycemic index, check out The Complete Idiot’s Guide to Glycemic Index Weight Loss or The Glycemic Index Diet for Dummies.

Which diets are based on the glycemic index?

Several major diets feature a low-GI approach to weight loss. The Atkins diet has always followed a low-GI formula, and Atkins food products were developed with a patent-pending clinical method that substantiates the impact and confirms the accuracy of Atkins net carb label claims.

Nutrisystem is another major diet program that relies on the glycemic index. Unlike Jenny Craig and Weight Watchers, Nutrisystem’s meals are all low-GI, taking the guesswork out of a low-GI diet. The South Beach Diet’s induction phase is designed to eliminate cravings for carbs and refined starches, stabilizing blood sugar in the process. Gradually foods with a slightly higher glycemic index value are reintroduced, and the maintenance phase of South Beach encourages followers to contain selecting low-GI foods.

How do I use the glycemic index?

Many healthy foods have a higher GI ranking (watermelon, dates, parsnips), so dieters without diabetes should remember that the index doesn’t need to be followed unwaveringly.

Low-GI foods tend to be more nutritious and satiating and may aid your weight loss efforts, so the next time you’re at the supermarket, consider tossing some low-GI foods into your cart. And visit to find out the glycemic value of your favorite foods.

Are there any times when it is good to eat high glycemic foods?

Athletes can benefit from consuming high glycemic foods after exercise sessions to replenish lowered glycogen levels after extensive and/or exhaustive aerobic exercise. Low-glycemic food selections are recommended for athletes prior to exercise sessions. Choose the healthiest options among high-glycemic foods to acquire adequate nutrients, such as baked beans, bran, wheat bread, fruit cocktail, grapefruit juice, grapes, green peas, orange juice, sweet potatoes and yams.

What is the glycemic load?

The Glycemic Load takes you one step further than the Glycemic Index by taking into account how much carbohydrate is in a standard serving size of food. The glycemic load offers a more accurate assessment of the  impact a food will likely create when it's consumed.

The glycemic load of foods are also numerically rated. 20 is considered high, 11-19 is medium, and 10 or less is low.
Most low GL foods have a low GI. Medium to high GL foods can be anywhere on the GI scale. The watermelon presents an interesting comparison. The glycemic index of a watermelon is 72, which is high. This is the measurement of its carbohydrate glycemic rate.

But watermelon is mostly water, and it's relative carbohydrate content is very low. The glycemic load of watermelon is four, which is very low. The glycemic load of a food is calculated by multiplying the glycemic index by the amount of carbohydrate in grams and dividing the total by 100.

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