Fad diets and obesity--Part II: An introduction to the theory behind low-carbohydrate diets.

Low-carbohydrate diets are not only highly popular but also controversial. The theory or general concept behind the low-carbohydrate dietary approach needs to receive more attention to provide more objectivity to this discussion. The theory or concept that actually has some evidence currently lies in the values of the glycemic index (GI) and glycemic load (GL). Basically, the higher the GI, the greater the glucose response. However, the GI system that was originally proffered in 1981 comes with one apparent limitation in that some foods or beverages need to be obtained in enormous amounts in order to observe such a glucose change. Therefore, the newer concept of GL (derived from the GI) is based on a more moderate-portion size and the resultant glucose change with some of the higher GI foods or beverages actually demonstrating a low GL. These and other limitations and some advantages of low-carbohydrate diets with an emphasis of what an actual GI or GL means are discussed.