A Significantly enriched or depleted microbial KEGG pathways from pathway enrichment analysis. Pathways in orange: cachexia-enriched; green: cachexia-depleted. CPM: copies per million. B Heatmap of Spearman’s rank correlation analysis between significantly enriched pathways versus differentially abundant metabolites (*p < 0.05, **p < 0.01, ***p < 0.001, +FDR < 0.1, ++FDR < 0.05, +++FDR < 0.01, Spearman’s rank correlation). Both differentially abundant MetaCyc pathways and significant KEGG pathways from enrichment analysis were used here. C Receiver operating characteristic (ROC) curve plots of Random Forest models based on the gut microbial taxonomic and pathway features of cancer patients for differentiating lung cancer patients with and without cachexia.