Your blood sugar level rises immediately after eating a meal or snack (Figure 2). In a healthy person, insulin then starts working, and the blood sugar level returns to the pre-meal level 2 hours after eating. In untreated diabetes patients, the blood sugar level does not return to the pre-meal level of its own accord. Some people's blood sugar level remains high two hours after eating, even though on an empty stomach it would be at a normal level. As a result, the risk of developing diabetes increases as insulin is not properly secreted, or does not work properly in the body. In order to make sure insulin works properly, it is important not to overeat and to avoid becoming obese. Knowing which foods will not cause a sudden and extreme spike in blood sugar level and using this knowledge in your daily life will help you to prevent obesity and diabetes, and maintain good health. In general, foods that cause blood sugar level to rise the most are those that are high in carbohydrates, which are quickly converted into energy, such as rice, bread, fruits and sugar. Next are foods high in protein, such as meats, fish eggs, milk and dairy products, and oily foods. However, even though carbohydrates affect blood sugar levels, if you don't eat them your diet will be unbalanced and you won't feel satisfied after your meal, which can lead to excessive consumption of foods rich in protein and fat. Carbohydrates do raise blood sugar levels quickly. However, recent studies have shown that even amongst foods that have the same amount of carbohydrates, there are two categories: those that cause a sudden rise in blood sugar levels and those that cause a more moderate rise, depending on the amount of dietary fiber contained. Taking bread as an example, whole grain rye bread and pizza crusts are low GI foods, while French bread and bagels are high GI foods. Because high GI foods cause a sudden spike in the blood sugar level, large amounts of insulin are secreted in order to process the sugar in the blood, causing a spike in insulin secretion to handle the sugar. When low GI foods are eaten, the sugar is gradually absorbed into the body so the blood sugar level rises gradually. Thus, an appropriate amount of insulin is secreted and sugar is promptly taken up by the tissues.