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. 2025 Jul 18:12:1573199.
doi: 10.3389/fnut.2025.1573199. eCollection 2025.

Association between the dietary index for gut microbiota and frailty: the mediating role of body mass index

Jiawei Lei #  1 , Tingting Feng #  1 , Tian Tian #  1 , Ziyun Zhuang  2 , Guilei Zhang  1 , Ying Liu  3 , Zhenrong Yang  1 , Yuting Wang  4 , Xin Zhang  5 , Wei Sun  6 , Jiahe Wang  1
Affiliations

Association between the dietary index for gut microbiota and frailty: the mediating role of body mass index

Jiawei Lei et al. Front Nutr. .

Abstract

Background: The Dietary Index for Gut Microbiota (DI-GM), a newly introduced metric, indicates gut microbiota diversity. However, its correlation with frailty remains unexplored.

Method: A total of 25,320 individuals were included in the 2007-2020 National Health and Nutrition Examination Survey (NHANES). Dietary recall data were calculated by averaging intake values from two separate 24-h dietary recall interviews. Frailty was assessed using the 49-item frailty index. The relationship between DI-GM and the frailty phenomenon was examined by applying a weighted logistic regression model. A comprehensive sensitivity analysis was undertaken, incorporating restricted cubic splines for modeling non-linear effects, stratified subgroup analyses to explore effect modification, and multiple imputation techniques to address potential missing data concerns.

Results: Higher DI-GM scores and gut microbiota-beneficial dietary components were significantly associated with reduced prevalence of frailty (Frailty Index: OR = 0.987, 95% CI: 0.977-0.997, P = 0.014; Frailty: OR = 0.941, 95% CI: 0.902-0.980, P = 0.004). Restricted cubic spline analysis revealed a non-linear relationship between DI-GM and frailty. Body Mass Index (BMI) mediated this relationship, accounting for 17.57% of the association.

Conclusion: We concluded that a higher DI-GM score is associated with a lower risk of frailty, partly via BMI mediation. Future research should validate these findings using longitudinal studies.

Keywords: NHANES; body mass index; diet; frailty; gut microbiota; mediation.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Flowchart depicting participant selection from NHANES 2007-2020. Initial 44,002 participants aged 20 or older, 6,084 excluded due to missing DI-GM components. Of 38,318 with data, 12,998 lacked covariates: 42 without educational level, 16 marital status, 3,711 PIR, 367 BMI, 8,852 physical activities, 10 medication data. Final count: 25,320 with complete data.
FIGURE 1
Flowchart of participants of the NHANES 2007–2020.
Three histograms with trend lines show odds ratios related to gut microbiota. Chart A presents a dietary index, with p-values: overall less than 0.001 and nonlinear equals 0.012. Chart B shows results for beneficial factors with p-values: overall less than 0.001 and nonlinear equals 0.833. Chart C illustrates unfavorable factors with p-values: overall equals 0.015 and nonlinear equals 0.127. Shaded areas indicate confidence intervals.
FIGURE 2
Association between DI-GM and frailty in NHANES 2007–2020 participants by RCS. (A) Restricted spline regression showed non-liner association between DI_GM and frailty. (B) Restricted spline regression showed liner association between Beneficial to gut microbiota and frailty. (C) Restricted spline regression showed liner association between Unfavorable to gut microbiota and frailty. Model adjusted for age, sex, race, education, BMI, PIR, PA total MET, take anti-infectives drugs. Frailty determines whether the Frailty index is ≥ 0.25.
Forest plot showing adjusted odds ratios (aOR) with 95% confidence intervals for various subgroups. Subgroups include age, sex, race, education, marital status, PIR, anti-infection drug use, and years from 2007 to 2020. Key findings are females aged over 50 and those above high school, having statistically significant aOR below one, indicating lower risk. P-values for interaction vary, with significant differences in education subgroup (p=0.004). Horizontal bars represent confidence intervals across different subgroups, centered around a vertical line indicating neutral risk at aOR=1.
FIGURE 3
Subgroup analysis of the association between DI-GM and frailty status. aOR, adjusted Odds Ratio; 95%CI, 95% Confidence Interval. Model adjusted for age, sex, race, education, BMI, PIR, PA total MET, take anti-infectives drugs.
A mediation analysis diagram shows the relationship between DI-GM and Frailty, with BMI as the mediator. Arrows indicate the causal pathways. The direct effect from DI-GM to Frailty is -0.00988, and the indirect effect through BMI is -0.00214. The total effect is -0.01210, with a mediation proportion of 17.57%. The confidence intervals and p-values are provided for statistical significance.
FIGURE 4
Mediation analysis of BMI in the association between DI-GM and Frailty. 95%CI, 95% Confidence Interval. Model adjusted for age, sex, race, education, PIR, PA total MET, take anti-infectives drugs.
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