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.