In lean subjects there are Coriobacteriaceae, Lactobacillus, Enterococcus, Faecalibacterium prausnitzii, Prevotella, Clostridium Eubacterium, E. coli and Staphilococcus. By contrast, Bifidobacterium, Methanobrevibacter, Xylanibacter, Bacteroides characterize the composition of lean gut microbiota.