The Glycemic Index
The glycemic index is a rating system that assigns a number to any given food designating the rate at which the sugars in that food produce an insulin response in the body. Foods are rated from 0 - 100. The higher the number, the more quickly that food raises blood sugar levels; low numbers are assigned to foods that raise blood sugar very slowly.
Glycemic index is not a measurement of the sugar a food contains, but rather the rate at which that food breaks down into glucose sugar in the body.
The Glycemic Index of Foods
Instant mashed potatoes have a high glycemic index, a whopping 87; honey has a glycemic index of 61; a raw apple, 36. Glycemic index ratings are 'raw' numbers, meaning that the foods are rated in their most basic state. The mashed potatoes had no added condiments when it was measured. If you add butter and sour cream, the glycemic index of those dehydrated potatoes will change. The GI will drop, in fact, because dietary fat slows down the breakdown of the complex sugars in the potato, thus slowing down the increase in insulin production.
Many factors, then, will affect the actual glycemic impact of the foods your eat. Keep this in mind as you use the glycemic index to plan your meals. There are individual differences that can't possibly be added to the equation as well. For example, your insulin response to foods may be affected by your age, activity levels, the time of day and your unique insulin sensitivity.
The Glycemic Index: A Tool for Healthy Eating & Weight Loss
Any one pursuing a weight loss diet or interested in weight management, disease prevention and long life, can benefit from just a rudimentary understanding of the glycemic index. We suggest only a basic understanding, because the science of glucose-insulin response is really quite complex. Here's what you need to know in order to benefit from using the glycemic index for weight loss, weight management or disease prevention:
Glycemic Index and Glycemic Load
The glycemic index has recently been improved with a second rating factor: glycemic load. Here is the difference between the two: glycemic index measures how quickly a particular food elevates blood sugar levels and then triggers an insulin response. The higher the number, the quicker the response. The glycemic index is looking at the carbohydrate content of the food, since that is the triggering food component relative to blood suger. A glycemic index of 70 or more is considered high, 56-69 is medium, and 55 or less is low.
The glycemic load of a food looks at more than the carbohydrate in a food, and takes into account how much carbohydrate a food contains. The glycemic load offers a more accurate assessment of the glucose/insulin 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. We find then, that the glycemic load of watermelon is 4, very low.
The Glycemic Index & Glycemic Load: Numbers & Charts
Next you need access to a comprehensive chart showing the glycemic index and glycemic load of foods. We have published several charts here. The University of Sydney has a searchable database on their web site glycemicindex.com.
Here is a chart of the glycemic index of foods.
The Glycemic Index: Why It's Important and How It Can Help
Blood sugar levels are important to maintain for a few reasons. First, there are the physical reactions and food cravings that result when levels that dip too low, which can result in lethargy, headache, dizziness, inability to concentrate and increased hunger. Your body may not need more food, but it does need more glucose, so it will motivate you to eat, and it usually wants high carb foods to feed the low glucose level.
When your blood sugar level is too high, your body produces insulin to bring that level down and stabilize the glucose content of your blood. When insulin is released into your blood, it converts the excess glucose into fat and it also signals to your body to store it's fat reserves. We find then, that high glycemic snacks and meals, even though they may initially offer an elevation in energy and mood, will inevitably result in fat storage and the crash that is experienced when our body is slammed with a high dose of insulin.
Low glycemic foods release glucose gradually into the bloodstream, which necessitate a modest amount of insulin production. Blood sugars remain stable and balanced. Energy levels, while not necessarily explosive, will be sustained and even. Your body will be more likely to burn fat reserves rather than use up the glucose in your blood. For dieters and those with diabetes, a diet rich in low glycemic foods is highly desirable. A low glycemic orientation can be applied to filely any weight loss diet. An increasing number of doctors, diet experts and nutritionists advocate using the glycemic index in conjunction with meal programs for the management of diabetes as well as for weight loss.
Related information on the glycemic index:
Glycemic Index Diets
Glycemic Index of Foods [chart]