A low carb diet is a slang expression for a 'low carbohydrate' diet. This is usually based on the Glycemic Index, which indexes carbohydrates relative to their effect on blood sugar levels. This is a controversial diet, although its medical benefits in terms of people suffering from some medical conditions are generally accepted in popular culture. There are however some doubts about low carb diets as a dietary option. Carbohydrates include simple sugars, starches, and other typical junk foods, but also include complex carbohydrates like grains, and other useful dietary items.