The Dietary Index for Gut Microbiota and Live Microbe Intake in Relation to Visceral Fat Obesity: Evidence From <scp>NHANES</scp> With Vitamin D as a Mediator

While the gut microbiota plays a critical role in host metabolism, epidemiological evidence linking microbiota-targeted dietary patterns to visceral fat obesity (VFO) remains limited. Using data from 8080 adults aged 20-59 years participating in the National Health and Nutrition Examination Survey (NHANES) 2011-2018, we examined the associations of the Dietary Index for Gut Microbiota (DI-GM) and dietary live microbe intake with visceral fat area (VFA) and VFO, and further explored the potential mediating role of serum vitamin D. Multivariable linear and logistic regression models were applied to assess associations with VFA and VFO, respectively, with restricted cubic spline analyses (RCS) used to evaluate potential non-linear relationships. Higher DI-GM quartiles were significantly associated with lower odds of VFO (Q4 vs. Q1, OR = 0.58; 95% CI: 0.43-0.79; <i>p</i> < 0.001), independent of demographic, lifestyle, and dietary covariates. Similar inverse associations were observed for higher dietary live microbe intake (G3 vs. G1, OR = 0.66; 95% CI: 0.55-0.81; <i>p</i> < 0.001). RCS analyses indicated an approximately linear inverse association between DI-GM and VFA (nonlinear <i>p</i> = 0.097) and a significant nonlinear inverse relationship between MedHi and VFA (nonlinear <i>p</i> < 0.001). Mediation analyses revealed that serum vitamin D partially mediated the associations between DI-GM and VFO (16.8% mediated, <i>p</i> < 0.001), and between dietary live microbe intake and VFO (17.0% mediated, <i>p</i> < 0.001). In summary, higher adherence to gut microbiota-targeted diets (DI-GM and live microbe intake) was associated with lower VFA and VFO, with serum vitamin D statistically mediating part of these associations. These findings highlight potential links among diet, vitamin D status, and VFO and warrant further investigation in longitudinal and interventional studies.