Here's a short extract
What is Glycemic Index?
Because of the profound impact on our health, scientists have started to investigate the physiological response of different foods on blood sugar levels. The glycemic index (GI) of food is a ranking of foods based on their immediate effect on blood glucose (blood sugar) levels.
The GI ranks a food on a scale from 0 to 100 according to the extent to which it raises blood sugar levels after eating. Carbohydrate foods that breakdown quickly during digestion have the highest glycemic index rating. Their blood sugar response is fast and high. The substance which produces the greatest rise in blood sugar is pure glucose. Therefore, the GI of glucose is 100.
Every other food is ranked between 100 and zero. Carbohydrates that breakdown slowly, releasing glucose gradually into the blood stream, have a low glycemic index(6). Foods with a high GI produce a great surge of glucose into the blood steam. This surge in blood glucose is matched by another in insulin in an attempt to control blood glucose levels.
High GI foods produce marked fluctuations in blood glucose levels. Low-GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood glucose and insulin levels, and have proven benefits for health.
Why is the GI factor so important?
Quite simply, by selecting foods with the GI factor in mind, you will decrease the amount of insulin secreted and promote insulin sensitivity within tissues. This adds up to making insulin more effective within your body.
The GI concept was first developed in 1981 by Dr. David Jenkins (a professor of nutrition at the University of Toronto, Canada) for diabetics as an aid to food selection to help insulin management. This initial work has been expended tremendously by scientists of the University of NSW, Sydney Australia and the GI factor is now a well renown nutritional strategy to help prevent and control type 2 diabetes, heart disease, and obesity (6).
For the drug-free bodybuilder, knowledge of the GI index of carbohydrate foods is invaluable.
It allows you to control and manipulate natural insulin secretion to obtain the maximum anabolic effect from your training.
Manipulating insulin levels in the hours after intense training will facilitate maximum nutrient transportation into muscles, accelerating recovery and cellular adaptation.
One of the hardest parts of fat loss for definition is feeling hungry all the time. This gnawing feeling is not necessary to lose fat. Low GI foods are natural appetite suppressants.
Controlling insulin by using the GI factor of foods ensures fat is burned and the anabolic drive is maintained all day, every day.
It's all in the digestion.
What makes one carbohydrate different to another in terms of its GI rating? This all has to do with the physical state of the carbohydrate in the food. When carbohydrates are consumed in their natural packaging, such as whole or intact grains, oats, barley, whole wheat and vegetables, the food will take longer to digest (break down) and its monosaccharides will enter the blood stream slowly. These foods will have a lower GI factor.
Therefore the whole grain or unprocessed food will always have more gradual, prolonged effect on blood sugar. (There are some exceptions to this, such as potatoes and different forms of white rice.)
The other aspect that governs digestion of a carbohydrate is the ratio of two different types of starches the food has. These two starches are called amylose and amylopectin.
To put it simply, amylopectin molecules are larger, more open and easier to digest. Thus, foods that have little amylose and plenty of amylopectin within there carbohydrate will be more rapidly digested and absorbed into the blood stream and will possess a higher GI number. Some examples of high amylopectin to amylose carbohydrate foods are wheat flour and Calrose white rice. These foods have high GI numbers.
Some foods that have more amylose than amylopectin are basmati white rice, durum wheat pastas and all sorts of legumes. Therefore, these carbs possess low GI numbers.
The sugar myth.
Many people believe a healthy diet means avoiding all sugar. Remember, sugar (sucrose) is two molecules jointed together (a disaccharide). Sugar is one molecule of glucose joined to one fructose molecule.
Fructose is the one single sugar which is an exception to the GI rule. To be made usable, fructose must travel to the liver, were it is slowly converted to glucose. So the blood sugar response to fructose is very small, it has a GI rating of only 20.
So when we consume normal sugar (sucrose), half of this is glucose and half is fructose. Sucrose has a GI rating of 60-65. Pure glucose has a GI rating of 100.
Compare this to another type of disaccharide called maltose, which is two glucose molecules joined together. Maltose has a very high GI of 95-100, quite a big difference to sucrose. Therefore, it pays to know the difference between your sugars.
Contrary to popular opinion, most foods containing "sugar" per se, do not raise blood sugar levels any greater than most breads or commercial cereals. Remember however, that volume is still important.
The GI rating of a food is based on the blood sugar reading obtained from 50 grams of that particular carbohydrate food.
While 50 grams of pure glucose (a refined carbohydrate) is a few spoons, it takes 700 grams (1 and a half pounds) of carrots to obtain 50 grams of carbohydrate. So if your names not Bugs Bunny, which food would you most easily consume excessive calories?
Weight loss and fat loss still comes down to the amount of calories you take in verses the amount you burn on a daily basis regardless of GI factor. However, by knowing the GI factor of carbohydrate foods makes it easier to avoid hunger pangs and stay within your caloric range and lose fat!
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(lots of fat!) i managed to bring the weight down to 205lb in the last 9 months with a low carb diet. I have no idea what my BF % is. Im sure i dont eat good to get some gains thats why i posted this message maybe you guys can help me out. I have no idea if this is good what i do.. its just what i heard.. please dont laugh 
heard this before on the board but can you or someone else explain me what that is?!
