Glycemic index (GI) is a ranking system for foods (specifically the carbohydrates contained therein) based on their effect on blood sugar levels in the first two hours. The concept was invented in 1981 by Dr. David J. Jenkins of the University of Toronto.
Foods with a high GI tend to raise quickly the blood sugar level in the body while foods with a low GI will slowly increase the blood sugar over a longer period of time.
Foods with a high GI value require less energy to be converted into glucose and will rapidly break down and raise the blood sugar. People who eat high-GI foods will feel hungry very soon. If this pattern is frequently repeated, one may end up with gaining in weight as a result of constantly overeating.
On the other hand, foods with a low GI value break down slowly and release sugar gradually into the blood stream. The body will digest and absorb the sugar and starch in the foods at a slower rate. It will help control appetite and delay hunger as people will feel fuller for longer and are less sooner to snack. In addition, a lower glycemic response equates to a lower insulin demand, better long-term blood glucose control and a reduction in blood lipids. It will benefit people with diabetes (type 1 and type 2), as suggested by various studies.
GI is a standardized system that runs from 0 to 100. There are basically 3 categories:
1. Low GI
55 or less, most fruit and vegetables (except potato), basmati rice, oats, all-bran will fall in this category.
2. Moderate GI
56 to 69, sucrose and Mars bar are some good examples.
3. High GI
70 or above, some representative examples are corn flakes, baked potato, jasmine rice, white bread.
A low GI diet will make you less susceptible to constipation due to high fiber content of low GI foods. Your blood cholesterol level and risk of heart disease will be reduced, too. It is also possible to help you lose or control your weight. More importantly, you need not starve as the diet enterprises of a balanced combination of proteins, carbohydrates and good fats.
Neverheless, foods with a low GI value may contain high contents of other undesired things such as salt. So relying solely on GI value is insufficient, you still need to take note of the nature of foods you eat. Moreover, it is also difficult to identify the GI value of a complete meal which may contain various types of food with different GI values. Some dietitians and nutritionists do caution that one should not totally avoid all high-GI foods. As a guideline, the more low GI foods that are included into a meal, the lower the overall GI value for that meal.