The investigators will study prevention effect of Life style modification on diabetes mellitus comparing with conventional management and Metformin administration.

Inclusion Criteria:

1. 30<Age<71
2. BMI≥23 kg/m2
3. '75g Oral glucose tolerance 2 hours after the test Blood glucose140~199mg/dL' or 'Fasting Blood Sugar 110~125 mg/dL' or 'HbA1c 5.7%~6.4%'

Exclusion Criteria:

1. Who diagnosed with Diabetes Mellitus or Who having Drugs for Diabetes Mellitus.

2. Type 2 Diabetes Mellitus

   • Who diagnosed with Diabetes Mellitus except for maternity period.
   • Who have had drugs for Diabetes Mellitus(hypoglycemic agent or insulin) except for maternity period.
   • Fasting Glucose≥ 126 mg/dL
   • 75g Oral glucose tolerance 2 hours after the Blood glucose ≥ 200 mg/dL
   • HbA1c ≥ 6.5%

3. Who life expectancy is short.

   • Cardiac history

     • History of severe cardiovascular disease within the last 6 months (cerebral hemorrhage, stroke, myocardial infarction, angina pectoris, heart failure, etc.)
     • Systolic blood pressure >180 mmHg or Diastolic blood pressure >105 mmHg
     • aortic stenosis
     • Left bundle branch block or Third degree AV block

   • Who had been diagnosed and treated for malignant tumors including leukemia and lymphoma within the last 5 years

   • Abnormal renal function (Creatinine ≥ 1.4 mg/dL (male) or ≥ 1.3 mg/dL (female) or Urine Protein ≥ 2 +)

   • Anemia(Hematocrit <36%((male) or><33%(female)) ⑤ Cirrhosis or chronic active hepatitis (AST/ALT>３UNL)

   • Acute gastrointestinal disease (pancreatitis, infectious intestinal disease)

   • Who is scheduled major surgery within the last 3 to 6 months or just after the surgery.

   • Chronic infection (HIV, active tuberculosis, etc.)

   • Pulmonary patients who rely on oxygen or daily bronchodilators

4. Who is judged to be able to influence the clinical trial by investigator.

   • Who can not communicate
   • Those with psychiatric or cognitive impairment that may affect the compliance of the clinical trial
   • Those who do not agree to the treatment group allocation by random assignment
   • Those who participate in other studies that may interfere with the clinical trial
   • Those who lost weight by more than 10% during the past 6 months, excluding weight loss after giving birth
   • Those who can not have normal walking or exercise
   • Women who are pregnant
   • Those who are currently pregnant or who are within the last 3 months after giving birth
   • Those planning pregnancy during the clinical trial period
   • Those who have a history of drug and alcohol abuse (acute, chronic) within the last 2 years
   • Those who are not appropriate or unreliable for clinical trials at the discretion of the tester

5. Who taking medication or medical condition that may affect the diagnosis of diabetes

   • Thiazide diuretics
   • Systemic beta blockers
   • Taking Niacin for the treatment of neutropenic depression
   • Possibility of taking or injecting a systemic steroid preparation
   • Taking a serotonin reuptake inhibitor (SSRI) for weight loss purpose.
   • Taking medicine for weight loss
   • Hormone status is not appropriate during thyroid hormone replacement therapy (TSH abnormal range) (If thyroid hormone therapy is stable for more than 3 months and TSH is normal, the patient can participate in)
   • Others with other endocrine diseases (eg Cushing's syndrome, acromegaly)
   • During treatment, fasting plasma triglyceride> 600 mg / dL