Obesity has become an increasingly severe problem in modern society. The present application discloses methods for making obesity animal models, and the application of such obesity animal models on screening microorganisms, compounds, compositions, drugs, food, formulations or recipes, medicines, nutritional supplements, health care products, or beverages for their role in causing, preventing or treating the obesity. A method for establishing an obesity mouse model is disclosed, comprising, inoculating a germ-free mouse with an Enterobacter cloacae B29 having a 16S rRNA gene to provide an inoculated mouse, wherein the sequence of the 16S rRNA gene is at least 95% identical to SEQ ID NO.1; while feeding the inoculated mouse with a diet having 34.9 wt% of fat content for a period of time to provide an obesity mouse model, wherein the obesity mouse model manifests a metabolic syndrome, the Enterobacter cloacae B29 is capable of colonizing in the germ-free mouse's gut.
