Glycemic Index vs. Glycemic Load

The Glycemic Index has been well studied by health experts but has recently been popularized by diet gurus like Barry Sears as an integral tool for effective weight loss. Today, it's nearly impossible to find a diet-related book that doesn't give mention of the Glycemic Index. But what doesn't get nearly as much attention is the Glycemic Load of food. While it is equally as important as the Glycemic Index, becoming well acquinted with both is ideal.

What is the Glycemic Index?
The Glycemic Index is a ranking system for carbohydrates based on their effect on blood glucose levels. It was developed in 1982 by scientists to accurately describe how quickly a carbohydrate converts to sugar and is released into the blood stream. Food is rated on a scale of 0-100, with pure sugar topping the charts as the highest GI food.

How does it work?
ALL carbohydrates turn into some form of sugar (glucose) in your body. When you eat food containing carbohydrates, the carbohydrates are broken down into sugar (glucose) during digestion and then released into your bloodstream. As your blood glucose rises, your pancreas secretes insulin to help shuttle the glucose out of the blood and into the cells. This increase in insulin production and blood glucose is often described as a "sugar rush" or "spike". The speed at which your food increases your blood glucose level is referred to as the "glycemic response". Choosing food with a low Glycemic Index (<55) will produce a minor fluctuation of blood glucose levels. Often times after eating a high GI food (>70) you'll experience a short surge of energy followed by an equally powerful crash as your blood sugar plummets. This is a vicious cycle that can lead to weight gain because you'll often reach for more food when the "high" wears off.

Why should you care about Glycemic Index?
Adhering to foods with a low (<55) or medium (56-69) glycemic index will help stabilize blood sugar and keep you from riding the energy roller coaster. Typically, foods with a low GI, like fruit and vegetables, have more fiber which will help keep you full longer between meals. This is why low GI foods are commonly recommended for individuals that are trying to lose weight. More importantly, these foods are more nutritious than their sugary and refined counterparts. When it comes to weight loss, it's best to limit the amounts of the higher GI foods and load up on the low-to-medium GI ones.

What about Glycemic Load?
The glycemic index compares the potential of foods containing the same amount of carbohydrate to raise blood glucose. However, the amount of carbohydrate consumed also affects blood glucose levels and insulin responses. 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. The Glycemic Load gives you a more complete picture as it takes into account the quality (glycemic index) as well as the portion size of a carbohydrate in a meal. This means that if eaten in smaller quantities, a high GI food can actually have a low GL and be pretty harmless.

Calculating Glycemic Load
White Potato:
GI is 85 (high)
GL= (34g x 85)/100
The Glycemic Load is 29

This illustrates how the ranking system for GL factors in the portion size as well as the GI to provide a more useful measure of a carbohydrates effect of blood glucose.

Glycemic Index of Vegetables (low-high):
Broccoli 10
Cabbage 10
Lettuce 10
Mushrooms 10
Onions 10
Red Peppers 10
Carrots 49
Green peas 48
Corn, fresh 60
Beets 64
Pumpkin 75
Parsnips 97

Glycemic Index of Fruit (low-high):
Cherries 22
Grapefruit 25
Prunes 29
Apple 38
Pear 38
Plum 39
Strawberries 40
Orange 42
Peach 42
Grapes 46
Papaya 56
Banana 52
Kiwi 58
Mango 51
Apricots 57
Figs, dried 61
Raisins 56
Cantaloupe 65
Pineapple 66
Watermelon 72
Dates 103

Have you experimented with the Glycemic Index? Share your thoughts in comments.