Because diabetes is a disease for which there are abnormalities of metabolism such as carbohydrates. If there are, the better the eating as much sugar your body metabolism is all the result of high blood sugar levels body.
Since Diabetes is a disorder of the metabolism of dietary carbohydrates. If I eat a lot of sugar can burn out the body, resulting in high blood sugar levels.
Because diabetes is a disease with disorders of metabolism of carbohydrates. If you eat a lot of sugar body not burn out resulting in the body with high blood sugar.