OBJECTIVE: Intestinal microbiota have been suggested to contribute to development of obesity, but the mechanism remains elusive. We relationship between microbiota composition, intestinal permeability, inflammation in non-obese and obese subjects. DESIGN AND METHODS: Fecal microbiota composition of 28 subjects (BMI 18.6-60.3kg/m2 ) was analyzed phylogenetic profiling microarray. Fecal calprotectin and plasma C- protein levels were determined to evaluate intestinal and systemic Furthermore, HbA1c , and plasma levels of transaminases and lipids were Gastroduodenal, small intestinal, and colonic permeability were assessed multi-saccharide test. RESULTS: Based on microbiota composition, the population segregated into two clusters with predominantly obese (15/19) exclusively non-obese (9/9) subjects. Whereas intestinal permeability differ between clusters, the obese cluster showed reduced bacterial decreased Bacteroidetes/Firmicutes ratio, and an increased abundance of pro-inflammatory Proteobacteria. Interestingly, fecal calprotectin was detectable in subjects within the obese microbiota cluster (n=8/19, Plasma C-reactive protein was also increased in these subjects correlated with the Bacteroidetes/Firmicutes ratio (rs =-0.41, p=0.03). CONCLUSIONS: Intestinal microbiota alterations in obese subjects are with local and systemic inflammation, suggesting that the obesity- microbiota composition has a pro-inflammatory effect.