Medical nutrition therapy is the first line of treatment for the prevention and management of type 2 diabetes and plays an essential part in the management of type 1 diabetes. Although traditionally advice was focused on carbohydrate quantification, it is now clear that both the amount and type of carbohydrate are important in predicting an individual's glycemic response to a meal. Diets based on carbohydrate foods that are more slowly digested, absorbed, and metabolized (i.e., low glycemic index [GI] diets) have been associated with a reduced risk of type 2 diabetes and cardiovascular disease, whereas intervention studies have shown improvements in insulin sensitivity and glycated hemoglobin concentrations in people with diabetes following a low GI diet. Research also suggests that low GI diets may assist with weight management through effects on satiety and fuel partitioning. These findings, together with the fact that there are no demonstrated negative effects of a low GI diet, suggest that the GI should be an important consideration in the dietary management and prevention of diabetes.