NMR metabolomic signatures of healthy lifestyle and incident MASLD.

We aimed to investigate the relationship between metabolomic signatures of healthy lifestyle with incident metabolic dysfunction-associated steatotic liver disease (MASLD) risk, and quantify the extent to metabolic signatures explain the healthy lifestyle-MASLD relationship. This prospective cohort study analyzed 179,261 UK Biobank participants with available nuclear magnetic resonance metabolomics data. Healthy lifestyle scores incorporated dietary quality, alcohol consumption, physical activity, and smoking behavior. Elastic net regularized regression identified lifestyle-associated metabolic signatures from 251 metabolic biomarkers. Cox regression models evaluated associations between lifestyle indices, metabolic profiles, and incident MASLD. Counterfactual-based mediation analysis quantified mechanistic pathways. During follow-up, 2422 participants (1.35%) developed incident MASLD. We identified a 94-metabolite signature strongly reflecting healthy lifestyle behaviors, dominated by lipoprotein subclasses (61.70%) and fatty acids (10.64%). Each 1-unit increment in the metabolic signature corresponded to 65.9% reduced MASLD risk (HR = 0.341, 95% CI 0.311-0.373). Mediation analysis revealed that metabolic alterations explained 55.80% (95% CI 47.85-85.28%) of the protective lifestyle-MASLD association, with fatty acid metabolism contributing the largest mediation effect. Addtionly, the parallel mediating effect of metabolic signatures, BMI, diabetes, and hypertension reached 86.21%. This comprehensive metabolomic signature captures healthy lifestyle behaviors and strongly predicts incident MASLD risk through metabolic reprogramming, particularly fatty acid and lipoprotein metabolism.