Increased fecal glycocholic acid levels correlate with obesity in conjunction with the depletion of archaea: the DOSANCO Health Study.

Background: Recent studies have focused on the relationship between obesity and gut microbiota. This study aims to identify fecal components and gut bacterial species associated with different BMI categories.

Methods: In this study, 538 participants aged ≥18 years were categorized into underweight, normal, and obese groups based on BMI (cutoffs: 18.5 and 25.0 kg/m²). We compared 30 fecal components among these groups and calculated correlation coefficients between each component and BMI. Participants were then divided into quartiles based on fecal component levels correlated with BMI, and the prevalence ratio (PR) of obesity was calculated, adjusted for confounding factors. We also analyzed the composition and diversity of gut microbiota and bacterial gene expression among the quartiles for each fecal component.

Results: Fecal glycocholic acid (GCA) showed a significant positive correlation with BMI. The PR for obesity in the highest quartile of fecal GCA was 3.30 (95% CI: 1.21-9.54), indicating a significantly higher risk of obesity compared to the lowest quartile. Gut microbiota analysis revealed significant differences in the abundance of Ruminococcaceae Incertae Sedis, Faecalibacterium, and Methanobrevibacter, with Methanobrevibacter being absent in the higher quartiles of fecal GCA. Additionally, gene expression for enzymes involved in the deconjugation of conjugated bile acids, including GCA, was downregulated in the highest quartile.

Conclusions: Increased fecal GCA levels are positively correlated with obesity, alongside a depletion of archaea.