The glycemia is the measurement of the level of sugar (glucose) in the blood. The glycemic index makes it possible to classify foods according to the elevation of the glycemia which they produce when they are consumed. The higher their index, the more the food causes a rapid rise in the sugar level . This immediately causes a strong secretion of insulin , whose role is to lower the sugar level. Thus, a food with a high glycemic index quickly causes a drop in sugar levels as a result of the action of insulin. This drop in sugar then increases hunger. Foods with a high glycemic index are therefore more likely to make you fat because they stimulate your appetite.
Are classified hyperglycemic (index of more than 50), for example, quick-cooking rice (85), white bread (70) and bananas (60). Foods with a low glycemic index include oatmeal (40), dried figs (35) and green beans (30). Obviously, you don’t have to worry about the glycemic index for all foods that don’t contain carbohydrates, like meats and fish.
The glycemic index of the same food can vary depending on several factors. Take the example of a cereal, say wheat. The more the grain of wheat is finely ground, the more its glycemic index increases. This is why the bread of wheat, made of a fine flour, increases blood sugar (and fat storage) more than the pasta , made of semolina , a coarser ground grain. Likewise, refined flour has a higher glycemic index than whole flour. Finally, an industrial treatment like pre-cooking also raises the glycemic index of a cereal. It should also be noted that different varieties of the same food may have different glycemic indexes.
A relatively new concept in nutrition, the glycemic load completes the glycemic index well. While the glycemic index only gives the measure of the quality of carbohydrates , the glycemic load also considers the quantity real of these carbohydrates in a normal portion . It also takes into account the “anti-glycemic” effect of dietary fiber in foods. Thus, even if the watermelon has a very high glycemic index (72), its glycemic load for a normal portion of 150 g is only 5. In return , the glycemic load of a refined food, such as white rice, can exceed 25 for a 150 g serving. A single portion of white rice therefore provides the same glycemic load as 5 portions of watermelon.
The glycemic load of each food is indicated in the files of our Encyclopedia of food .
- Zero : no glycemic load
- Low : glycemic load of 10 or less
- Moderate : glycemic load from 11 to 19
- Strong : glycemic load of 20 and more
It is quite obvious that foods with glycemic index or at glycemic load are likely to upset the glycemia. In the long term, their high consumption is associated with an increased risk of type 2 diabetes and cardiovascular disease. In addition, foods with a low glycemic index generally satiate better, which helps to avoid being hungry or overeating.
In athletes, the glycemic index of a food can influence performance. In general, if a snack is taken one hour before exercise, eating food with a high glycemic index is a priority. On the other hand, for a long-term training, foods with a low glycemic index are more interesting because they cause a less rapid but lasting energy release over time. After exercise, eating foods with a high glycemic index facilitate recovery.
If it is interesting to trust the index and the glycemic load of a food, it should not be forgotten that during a meal, one ingests at the same time several foods including indexes differ. You should also be aware that dietary fiber (and proteins and fats, but to a lesser extent) lowers the glycemic index.
Foster-Powell K, Holt SH, Brand-Miller JC. International table of glycemic index and glycemic load values, Am J Clin Nutr . 2002 Jul; 76 (1): 5-56. [Accessed August 26, 2010]. www.ajcn.org