Top 10 species with the highest relative abundance of the 5 groups at the level of phylum. The top 5 phyla were Bacteroidetes, Firmicutes, Fusobacteria, Proteobacteria and Actinobacteria. No statistically significant differences were identified among species at the level of phylum. However, a decreasing trend of Bacteroidetes and an increasing trend of Fusobacteria was determined in the CO group compared with that in the SG0 group (P=0.28 for Bacteroidetes and P=0.32 for Fusobacteria) and RYGB0 group (P=0.48 for Bacteroidetes and P=0.37 for Fusobacteria). An increasing trend of Bacteroidetes was identified in the SG3 group (P=0.49) and RYGB3 group (P=0.53) compared with that in the SG0 group and the RYGB0 group. CO, control group; SG, sleeve gastrectomy; RYGB, Roux-en-Y gastric bypass; SG0/3, group prior to/3 months after SG.