Accumulating evidence indicates that gut microbiota may play a pivotal role in onset and progression of obesity and insulin resistance, the core conditions of metabolic syndrome (MetS) via two different but complementary pathways, i.e.regulation of energy metabolism and provocation of chronic inflammation.However,these mechanistic findings are obtained almost exclusively with rodent models.Their relevance to humans still remains a question.It is also controversial whether the obesity-associated changes of gut microbiota happen at broad taxonomic-level or are more relevant with specific phylotypes.