Classifying the glycemic responses of carbohydrate foods using the glycemic index (GI) requires standardized methodology for valid results. Dietary carbohydrates influence metabolism by at least four mechanisms: nature of the monosaccharides absorbed, amount of carbohydrate consumed, rate of absorption, and colonic fermentation. Reducing glycemic responses by reducing carbohydrate intake increases postprandial serum free-fatty acids (FFA) and does not improve overall glycemic control in diabetic subjects. By contrast, low-GI diets reduce serum FFA and improve glycemic control. Thus, current evidence supports FAO/WHO recommendations to maintain a high-carbohydrate diet and choose low-GI starchy foods.