Abstract: Objective: To evaluate the efficacy of fermented milk containing Bifidobacterium animalis subsp. lactis MN-Gup in reducing body fat in individuals with simple obesity. Methods: A randomized, double-blind, placebo-controlled clinical trial was conducted in 60 adults with simple obesity. Participants were randomly assigned to receive either fermented milk containing MN-Gup or a regular fermented milk. After a 12-week intervention, changes in body composition, inflammatory markers, blood hormones, and gut microbiota were assessed. Results: The MN-Gup group showed significant extremely reductions in body weight, body mass index (BMI) and visceral fat areas compared with baseline (P<0.01). Body fat percentage and tumor necrosis factor-α (TNF-α) levels were significant reduced (P<0.05). Levels of glucagon-like peptide-1 (GLP-1) increased significantly in the MN-Gup group compared with baseline (P<0.05). The relative abundance of Bifidobacterium, Romboutsia, and Blautia increased extremely significantly, whereas the abundance of Enterobacter decreased extremely significantly in the MN-Gup group (P<0.01). Conclusion: Intervention with MN-Gup fermented milk can significantly improve body fat in individuals with simple obesity, providing a theoretical basis for the application of MN-Gup fermented milk.