Gut species Porphyromonas asaccharolytica and Bacteroides fragilis are associated with host body fat percentage, with MR analysis suggesting P. asaccharolytica may influence body fat percentage in part through its potential effect on B. fragilis abundance.
Porphyromonas asaccharolytica was negatively associated with whole body fat percentage (PFAT) in a US male cohort.
Bacteroides fragilis was positively associated with whole body fat percentage (PFAT) in a US male cohort.
Mendelian randomization analysis suggested a potential directional relationship between P. asaccharolytica and PFAT mediated in part through B. fragilis abundance.
The study used a comprehensive integrative analysis combining metagenomics and whole-genome sequencing data in a US cohort of men.
The associations between gut microbiota species and body fat percentage were consistent across two independent cohorts of different ethnicities.
This research suggests that two specific gut bacteria are linked to how much body fat a person carries. In a study of US men using advanced genomic analysis, researchers found that higher levels of Porphyromonas asaccharolytica in the gut were associated with lower body fat percentage, while higher levels of Bacteroides fragilis were associated with higher body fat percentage. These findings were confirmed in a separate group of Chinese participants, suggesting the relationships hold across different populations. Using a statistical technique called Mendelian randomization — which uses genetic data to help assess whether relationships between variables are directional rather than just coincidental — the researchers found evidence that P. asaccharolytica may influence body fat partly by affecting the levels of B. fragilis in the gut. This suggests the two bacteria may work together or interact in ways that affect fat storage in the body. This research matters because obesity and excess body fat are associated with many health problems, and understanding which specific gut bacteria are involved could eventually point toward new approaches for managing body composition. However, these are associational and directional findings from observational and genetic analyses, and further research would be needed to fully understand the biological mechanisms by which these bacteria might influence fat metabolism in humans.
Tian B, Liu Y, Su K, Jiang L, Lin X, Qiu C, et al.. (2026). Gut species Porphyromonas asaccharolytica and Bacteroides fragilis are associated with whole body fat percentage.. Journal of applied microbiology. https://doi.org/10.1093/jambio/lxag117