The fact that metformin treatment has been associated with reduced risk of cancer and cardiovascular disease raises the possibility of a beneficial role of metformin for other age-related diseases. The actions of metformin resemble the effects of calorie restriction (CR) to some extent, and microarray analyses have shown that metformin induces a gene expression profile that aligns with that of CR in animal. The aim of the study is to investigate whether metformin treatment can induce dietary restriction-like state in human.

Sixty overweight subjects will be included in this study, and participants will be divided 3 groups (20 cases in each group)including metformin group (0.85, twice daily), standard diet group, and CR group. All subjects will be treated 6 months. At the end of this study, blood samples and muscle samples will be obtained.

Blood samples will be obtained from all individuals. blood lipids, inflammation markers, insulin, glucose, leptin,adiponectin, ala aminotransferase, asp aminotransferase, creatine phosphokinase,lactate dehydrogenase, alkaline phosphatase,bilirubin, cyclo-oxygenase, citrate synthase, renal function, leukocyte telomere length ratio, and telomerase activity will be measured before and after the treatments.Also, hyperinsulinemic-euglycemic clamp will be performed before and after the treatments. Muscle samples will be obtained by biopsy for 9 individuals (3 cases from each group) at the end of the study. Microarray analysis will be performed for the gene expression profile from the muscle samples. Other protein expressions such asadenosine monophosphate-activated protein kinase (AMPK), peroxisome proliferator-activated receptor coactivator 1a (PGC-1a) activity,will be checked by Western blot.

Inclusion Criteria:

• Overweight
• Male

Exclusion Criteria:

• Female
• Obesity
• Using any other drugs
• < 18 years old
• > 60 years old
• Mental disorders
• Surgery history for abdomen