Korean type 2 diabetic patients are known to differ from western diabetes because of their unique characteristics, such as non-obese but centrally obese anthropometry and relatively more insulin secretory defects than insulin resistance compared to western diabetic patients.

We recruited 1,646 diabetic patients in the present study and excluded the 45 patients with fasting C-peptide < 0.20 nmol/L. We had assessed insulin secretion by fasting serum C-peptide level and insulin resistance by short insulin tolerance test (Kitt; rate constant for plasma glucose disappearance, %/min) in the private diabetes clinic. The insulin secretory defect was divided by severe (C-peptide < 0.37 nmol/L), moderate (C-peptide 0.37~0.56 nmol/L), and normal (C-peptide ≥ 0.57 nmol/L) group. The insulin resistance was divided by insulin resistant (IR) (Kitt < 2.5 %/min) and insulin sensitive (IS) (Kitt ≥ 2.5 %/min) group.

We analysed the data of 1,601 type 2 diabetic patients (831 men and 770 women, age 56.5 ± 10.8 years, duration of diabetes 9.6 ± 7.3 years). The prevalence of BMI ≥ 25.0 kg/m² is 42.5% and BMI ≥ 23.0 kg/m² is 70.2%. The prevalence of abdominal obesity (waist ≥ 90 cm in men and 80 cm in women) is 45.2% (36.0% and 55.2%, respectively in men and women). Fasting C-peptide level is 0.64 ± 0.29 nmol/L and Kitt value is 2.03 ± 0.96%/min. According to fasting C-peptide level, the degree of insulin secretory defect were severe (13.1%), moderate (33.0%) and normal (53.9%). According to Kitt value, the IR group is 70.6% and the IS group is 29.4%.

Obese type 2 diabetes is markedly increasing in Korea. Therefore, the major problem in Korean type 2 diabetic patients is being changed into insulin resistance instead of insulin secretory defect.