# Association Between the Dietary Index for Gut Microbiota and Frailty: Mediating Role of Body Mass Index

## TL;DR

A healthier diet for gut microbiota is linked to lower frailty risk, partly explained by body mass index.

## Contribution

This study establishes a novel link between the Dietary Index for Gut Microbiota (DI-GM) and frailty, mediated by BMI.

## Key findings

- Higher DI-GM scores are associated with a 4% reduced odds of frailty per point increase.
- BMI partially mediates the relationship between DI-GM scores and frailty, accounting for 24.83% of the effect.
- A nonlinear relationship between DI-GM scores and frailty was identified.

## Abstract

Dietary composition and quality have been linked to the onset of frailty. Although the recently developed Dietary Index for Gut Microbiota (DI‐GM) offers a means to evaluate diet quality based on its impact on the gut microbiota, its relevance to frailty has yet to be determined. This cross‐sectional study utilized data from the NHANES collected between 2007 and 2020. DI‐GM scores were determined based on 14 dietary components, with higher scores indicating a diet more supportive of gut microbiota health. Frailty was evaluated using a validated 49‐item frailty index, with frailty defined as a score of 0.21 or higher. Weighted logistic regression, restricted cubic spline models, and mediation analyses were employed to examine the relationship between DI‐GM scores and frailty. A total of 27,026 eligible participants were included in the analysis. Higher DI‐GM scores were significantly associated with a lower risk of frailty. After full adjustment (Model 3), each one‐point increase in the DI‐GM scores corresponded to a 4% reduction in the odds of frailty (OR: 0.96, 95% CI: 0.92–1.00). Compared to the lowest quartile (Q1), individuals in the highest quartile (Q4) demonstrated significantly lower odds of frailty (OR: 0.81, 95% CI: 0.67–0.99). A nonlinear relationship between DI‐GM scores and frailty was identified (p for nonlinearity = 0.031). Age, sex, education level, and smoking status were found to potentially moderate this association. Mediation analyses further revealed that body mass index (BMI) partially mediated the relationship, accounting for 24.83% of the effect (p < 0.001). These results indicate that higher DI‐GM scores are linked to a lower risk of frailty, with BMI partially mediating this relationship. Future longitudinal studies are needed to establish causality and further investigate the underlying mechanisms.

This study demonstrates that higher DI‐GM scores are associated with a lower risk of frailty, with BMI partially mediating this relationship.