The glycemic index is a method of rating how quickly insulin levels rise in response to various foods being consumed, although it is the ratio between two main hormones that determine how your body will utilize the carbohydrates that you eat.
The first of these hormones is glucogon which helps mobilize nutrients, so when glucagon is higher than insulin more food will be used as building materials or fuel.
The second hormone, insulin, is the most important hormone for nutrient storage, and a high level of insulin means that more of the food you eat will be stored as fat.
In general, protein foods stimulate the release of glucagon while carbohydrates stimulate the release of insulin. Importantly, neither glucagon nor insulin is immediately released when fats or nonstarchy vegetables are eaten.
This being said, ALL foods eventually turn to glucose which stimulates insulin somewhat, but carbohydrates enter the bloodstream much faster than proteins and fats do and so it is carbohyrdrates that are of most concern when considering the glycemic response. We have divided carbohydrates into three categories (Most Favorable Carbohydrates, Favorable Carbohydrates, and Unfavorable Carbohydrates) which ROUGHLY correspond to their position on the glycemic index.
It is important to remember that the glycemic response is mediated by several factors;
1. Refining, processing and cooking can all increase the glycemic response. This includes fresh-squeezed fruit juice, tomato paste, bread, and so forth.
2. Fiber can reduce glycemic response, which is why some sources use "effective Carb" ratios to help you gauge how a meal containing carbohysdrates will affect your glycemic response. (This method subtracts the fiber grams contained within the food from the carbohydrate grams and you come out with the Effective carb ratio. )
3. Combining carbohydrates, even high glycemic, carbohydrates with protein and fat will help to moderate at least somewhat the glycemic response to the carbohydrate.
4. Just because a carb is low on the glycemic index does not mean it is good for you. Fructose is one example.
In other words it is neither wise nor essential to fixate on consuming foods according to how they are rated on the glycemic index. A better approach is one which focuses on the quality of foods consumed and then on selecting foods (and lifestyle choices) in such a way as to maintain more balanced insulin/blood sugar levels. The easiest way to do this would be to follow our 3 easy steps to improved health.