Recently, microbial changes in the human gut was proposed to be another possible cause of obesity and it was found that the gut microbes from fecal samples contained 3.3 million non-redundant microbial genes. However, it is still poorly understood how the dynamics and composition of the intestinal microbiota are affected by diet or other lifestyle factors. Moreover it has been difficult to characterize the composition of the human gut microbiota due to large variations between individuals.