Gut Microbiota Profile in Inflammatory Bowel Disease: Associations with Disease Activity, Dietary Fiber Intake, and Body Composition

Introduction: Gut microbiota alterations are linked to inflammatory bowel disease (IBD) pathogenesis and intestinal inflammation (Iliev et al., 2025). Their relationships with dietary fiber and body composition remain unclear. Objective: To assess the fecal microbiota of individuals with IBD and its associations with disease type and activity, body composition, and dietary intake. Methods: This cross-sectional study included adults with IBD. Clinical activity, anthropometry, body composition and habitual intake using a food frequency questionnaire were assessed. Microbiota was analyzed by sequencing the V3–V4 regions of the 16S rRNA gene. Alpha diversity, relative abundance, and correlations were investigated. Results: Twenty-nine individuals participated: 17 (58.6%) had ulcerative colitis, 12 (41.4%) had Crohn’s disease, 18 were in remission, and 11 had active disease. Overweight or obesity was observed in 58.6%, and all participants had high body fat. Fiber intake was below recommendations in 58.6%, with lower adequacy during remission (66.2% vs. 106.6%; p=0.04). Bacterial diversity and the abundance of major phyla did not differ by disease type or activity. Bacillota and Bacteroidota predominated, and Faecalibacterium was the most abundant genus. Streptococcus abundance was higher in active disease (0.25% vs. 0.03%; p=0.03). Roseburia correlated with total and insoluble fiber (r=0.47; p=0.01) and soluble fiber (r=0.41; p=0.03). Shannon and Simpson indices correlated with phase angle (r=-0.56; p=0.002 and r=0.52; p=0.004, respectively). Conclusion: Overall diversity did not differ by IBD type or activity; however, greater Streptococcus abundance in active disease suggests an inflammation-associated alteration. Associations of Roseburia with fiber intake and of diversity indices with phase angle suggest interplay among diet, body composition, and gut microbiota.

References: Iliev ID, Ananthakrishnan AN, Guo CJ. Nat. Rev. Microbiol. (2025) 23:509.