Gut microbes are crucial for human health, which are usually accumulated in urban wastewater systems. Seven wastewater treatment plants in Australia with distinct population obesity rates between 18% and 33% were selected for wastewater sampling and analysis. Human gut microbiome were detected using metagenomic sequencing to investigate their associations with the community obesity rate. To unravel this complex relationship, a range of algorithm models, including linear discriminant analysis effect size (LEfSe), similarity percentage analysis (SIMPER), statistical analysis of metagenomic profiles (STAMP), linear models for microarray and RNA-Seq data analysis (LIMMA), Relief, ratio approach for identifying differential abundance (RAIDA), least absolute shrinkage and selection operator (LASSO), support vector machine (SVM), Boruta, DESeq2 and analysis of compositions of microbiomes with bias correction (ANCOM-BC), were used to identify potential bacterial biomarkers for obesity in the w