Dietary index for gut microbiota (DIGM) and cardiometabolic, inflammatory, and gut–brain-related biomarkers in adults with obesity: a cross-sectional study

Background The gut microbiota plays an important role in metabolic homeostasis and systemic inflammation, and dietary habits are major determinants of its composition and function. This study investigated the association between adherence to the Dietary Index for Gut Microbiota (DIGM) and cardiometabolic, inflammatory, and gut microbiota-related biomarkers in adults with obesity. Methods In this cross-sectional study conducted from January to December 2025, 637 adults with obesity aged 20–55 years were recruited from clinics affiliated with Mansoura University, Egypt, through clinic-based recruitment and public advertisements. Dietary intake was assessed using a semi-quantitative food frequency questionnaire, and the DIGM score was calculated based on predefined favorable and unfavorable dietary components according to the original scoring framework. Participants were categorized into tertiles according to their DIGM score. Anthropometric measurements, blood pressure, glycemic indices, lipid profile, lipopolysaccharide (LPS) and brain-derived neurotrophic factor (BDNF) and C-reactive protein (CRP) were assessed. Multivariable analyses were adjusted for age, sex, body mass index (BMI), smoking status, physical activity, dietary energy intake, education, occupation, marital status, and history of depression. Results Higher DIGM adherence was associated with lower SBP and higher high density lipoprotein cholesterol (HDL-C) after multivariable adjustment. Participants in the highest DIGM tertile showed lower circulating LPS and CRP concentrations and higher BDNF levels compared with lower tertiles (all adjusted P < 0.001). In multivariable linear regression models adjusted for confounders, higher DIGM scores were independently associated with lower SBP (β = −0.057; 95% CI: −0.011 to − 0.006), higher HDL-C (β = 0.100; 95% CI: 0.004 to 0.011), higher BDNF (β = 0.504; 95% CI: 0.295 to 0.407), and lower LPS (β = −0.468; 95% CI: −0.208 to − 0.146) and CRP (β = −0.048; 95% CI: −0.028 to − 0.003). Conclusion Greater adherence to the DIGM was independently associated with a more favorable inflammatory profile, higher circulating BDNF concentrations, lower LPS and CRP levels, and lower blood pressure among adults with obesity. These findings suggest that dietary patterns characterized by higher DIGM adherence may be associated with cardiometabolic and inflammatory profiles. Further prospective studies incorporating direct assessment of gut microbiota composition, microbial metabolites, and clinical outcomes are warranted to clarify the underlying mechanisms and temporal relationships. Keywords: Gut microbiota, Diet score, Obesity, Inflammation, Blood pressure, BDNF, Metabolic profile, Cardiometabolic risk.