Abstract: Objective: To study the influence of obesity on insulin(INS) and C-peptide(CP) level of elderly patients with Type 2 diabetes.Methods: Sixty-one cases of type 2 diabetics were included in the observation group and 58 healthy people acted as controls.All the subjects underwent 75 g oral glucose tolerance test(OGTT),insulin release test,CP release test,and the insulin sensitivity index(ISI) was calculated.Results: The 1 h level of INS of the obese cases in the observation group was lower than those of the control group(P<0.05),INS and CP responses during the OGTT were similar in obese subjects of the two groups.The 1 h,2 h levels of INS,and 1 h,2 h,3 h levels of CP after sugar test were reduced in non-obese subjects of the two groups(P<0.05 to P< 0.01).The levels of INS,CP of all the points during INS and CP releasing tests were higher in the obese subjects of the two groups than those in the non-obese subjects(P<0.05 to P<0.01),but ISI reduced significantly in the non-obese subjects,compared with the obese subjects(P<0.01).Conclusions: Obese elderly patients with type 2 diabetics have adequate circulating insulin level,but marked insulin resistance(IR).Non-obese elderly patients with type 2 diabetic have a profound impairment in glucose-induced IR but mild resistance.