Fig. 2

Structural changes in the gut microbial communities. PCoA analysis (principal co-ordinates analysis), or principal coordinate analysis, is a non-binding data dimensionality reduction analysis method that can be used to study the similarity or difference in the composition of sample communities. (a) PCoA analysis based on Unweighted UniFrac distance algorithm; (b) PCoA analysis based on Weighted UniFrac distance algorithm; (c) PLS-DA analysis, This analysis method needs to group the tested samples according to categories, distinguish each group during calculation, ignore the random differences in the group, and have better sample differentiation performance when the observation factor is much larger than the total sample size. (d) Community analysis sunburst plot on phylum level: MCI and Non_MCI; (e) The Mann-Whitney U (M-W U) test was used to statistically test the Firmicutes/Bacteroidota ratio; MCI: obesity with cognitive impairment group; Non_MCI: obese but cognitively normal group; *P < 0.05