obesity and diabetes have become major public health issues in our country. the increasing prevalence of obesity and its association with diabetes might not only be explained by genetic contribution, nutritional habits or decreased physical activity. in addition, recent studies have focused on the intestinal microbiota as environmental factors that increase energy yield from diet, regulate synthesis of gut hormones, peripheral metabolism and systemic inflammatory tone. obesity is associated with substantial changes in composition of gut microbiota, suggesting that the development of obesity on some people may be due to these changes. existing evidence warrants further investigation of the microbial ecology oh the human gut and points to modification of the gut microbiota, by functional foods or antibiotics, as one means to treat and prevent obesity.