The Obesity–Periodontitis Axis: Microbial Mechanisms and Clinical Implications

Background: Obesity and periodontitis are two chronic inflammatory diseases with a bidirectional relationship possibly mediated by microbial and immunologic signaling pathways. This narrative review aims to investigate how microbial dysbiosis and inflammation link these diseases, focusing on the interactions between the oral and gut microbiomes. Materials and methods: Peer-reviewed studies (2015–2024) from PubMed, MEDLINE, Ovid and Google Scholar were selected for their relevance to microbial dysbiosis and inflammation, prioritizing clear methodology. Non-peer-reviewed sources or studies lacking microbial/inflammatory data were excluded. Conflicting results and methodological differences, including sampling and study design, were assessed qualitatively on the basis of coherence and methodological rigor. Results: Obesity has been shown to significantly alter the composition of the oral microbiome, characterized by reduced diversity and an increased Firmicutes/Bacteroidetes ratio. At the same time, periodontal pathogens such as Porphyromonas gingivalis can invade the gut, impair barrier function and promote systemic inflammation. Both diseases share common inflammatory pathways involving adipokines and immune-system dysregulation, creating a feedback loop that exacerbates disease progression in both conditions. Obesity also appears to impair the effectiveness of conventional periodontal treatments. Conclusions: The microbial axis between the oral cavity and the gut represents a central pathway in the complex interactions between obesity and periodontitis. This relationship involves microbial dysbiosis, bacterial translocation and shared inflammatory mechanisms that collectively contribute to disease progression. Clinical relevance: A better understanding of the relationship between obesity and periodontitis supports the development of customized treatment strategies for obese patients with periodontal disease. Future research should focus on developing targeted interventions that address both conditions simultaneously to improve patient outcomes and develop more effective prevention and treatment strategies.