HbA1c was recently adopted as a reliable indicator for screening diabetes. This study investigated the ability of nutrition consultation to prevent diabetes in overweight women (BMI 23 $kg/m^2$ or more) using HbA1c as an indicator. Twenty overweight and obese women (with $HbA1c{geq}5.7$%) completed the 12-week nutritional study, with individual and personalized nutrition counseling performed every 2 weeks. The main study guidelines involved the following: 1) reducing the intake of high fat foods and alcohol, 2) consuming a large amount of vegetables, 3) reducing the intake of simple sugars and empty-calorie foods, and 4) increasing physical activity to ${geq}30$ min/day. Anthropometric (height, weight, BMI, body muscle (kg), body fat (%), waist and hip circumference, blood pressure) and biochemical parameters (fasting blood sugar (FBS), HbA1c, lipid profiles, hs-CRP) were measured before and after the nutrition consultation. After 12 weeks, the HbA1c<5.7% group had significant decreases in BMI, WC, HC, WHR, HbA1c, hs-CRP and also dietary intake of energy (P<0.01), carbohydrates, lipids (P<0.01), proteins (P<0.01) and cholesterol was significantly decreased (P<0.05). In the HbA1c ${geq}5.7$% group, HbA1c, TC, LDL, NON-HDL, hs-CRP and dietary intake of energy, carbohydrate, lipid, protein, and cholesterol significantly decreased (P<0.05). These results suggest that nutrition consultation effectively helps to prevent diabetes in overweight and obese women after applying HbA1c standards. Overall, the improvement in all markers measured suggest that HbA1c is a good indicator for blood glucose regulation, helping to prevent diabetes.