Purpose: The contribution of intestinal bacterial strains (gut microbiota) in human metabolism and obesity is being increasingly recognized. The goal of this article was to provide a commentary on the clinical usefulness of these data. Methods: We performed a review of the currently available articles on PubMed. Findings: Because most of the data are based on germ-free animal research, translation to human disease may be difficult. However, changes in the intestinal bacterial composition and subsequent altered diversity have been associated with the presence of chronic low-grade inflammation, a known feature of insulin resistance and type 2 diabetes mellitus. Implications: It is still not proven whether intestinal bacteria play a causal role in glucose and lipid metabolism. Intervention studies including fecal transplantation and supplementation of single bacterial strains in humans might provide more insight. Moreover, prospective cohorts of healthy subjects using fecal samples collected at baseline can help to identify causally involved specific intestinal bacterial strains that drive aberrant human metabolism. Ultimately, it would be a great asset if potential diagnostic and therapeutic targets could be derived from this novel player in human cardiometabolism. (C) 2015 Elsevier HS Journals, Inc. All rights reserved.