OBJECTIVE -To determine whether a chronic low-glycemic index (LGI) diet, compared with a high-glycemic index (HGI) diet, has beneficial effects on plasma glucose control, lipid metabolism, total fat mass, and insulin resistance in type 2 diabetic patients.RESEARCH DESIGN AND METHODS -Twelve type 2 diabetic men were randomly allocated to two periods of 4 weeks of an LGI or HGI carbohydrate diet separated by a 4-week washout interval, in a crossover design. RESULTS -TheLGI diet induced lower postprandial plasma glucose and insulin profiles and areas under the curve than after the HGI diet. At the end of the two dietary periods, the 7-day dietary records demonstrated equal daily total energy and macronutrient intake. Body weight and total fat mass were comparable. Four-week LGI versus HGI diet induced improvement of fasting plasma glucose (P Ͻ 0.01, ⌬ changes during LGI vs. HGI), HbA 1c (P Ͻ 0.01), and whole-body glucose utilization measured by the euglycemic-hyperinsulinemic clamp (P Ͻ 0.05).LGI diet induced a decrease in fasting plasma total and LDL cholesterol (⌬ changes LGI vs. HGI, P Ͻ 0.01), free fatty acids (P Ͻ 0.01), apolipoprotein B, and plasminogen activator inhibitor 1 activity. CONCLUSIONS -Only 4 weeks of anLGI diet was able to improve glycemic control, glucose utilization, some lipid profiles, and the capacity for fibrinolysis in type 2 diabetes. Even if changes in glycemic control were modest during the 4-week period, the use of an LGI diet in a longer-term manner might play an important role in the treatment and prevention of diabetes and related disorders. Diabetes Care 27:1866 -1872, 2004D iabetes is a chronic evolving disease associated with a variety of microand macrovascular complications. Increasing postprandial plasma glucose and insulin excursions are assumed (1,2) to increase severity of diabetes and to be independent predictors of risk for atherosclerotic diseases. As such, interventions to reduce postprandial plasma glucose and insulin peaks are one of the essential therapeutic objectives for diabetic patients and could reduce the risk of developing cardiovascular complications.Because dietary carbohydrate is one of the main factors in controlling postprandial hyperglycemia, it is reasonable to question whether the type of dietary carbohydrate can modify the evolution and complications of this disease in a clinically significant long-term fashion.There is growing recognition that the postprandial glycemic (3,4) and insulinemic (5) responses to different foods may vary despite equal amounts of total absorbable carbohydrates. This concept favors the use of low-glycemic index (LGI) carbohydrates. Although focusing on the total amount of carbohydrate intake is important for diabetic patients (6,7), using LGI carbohydrates could lead to additional benefits without increasing the fat content of the diet and consequently increasing plasma free fatty acids (FFAs), with all their deleterious consequences (8).Whether the glycemic index (GI) of foods has relevance to human health has been a topic o...