Ultra-processed foods and advanced stages of sarcopenia: multinomial evidence from the Birjand longitudinal ageing study

BACKGROUND: Sarcopenia, the age-related loss of muscle mass and strength, contributes to frailty and disability. Ultra-processed foods (UPFs) may increase risk via metabolic and inflammatory pathways. This study examined the association between UPF intake and sarcopenia in older Iranian adults. METHODS: This cross-sectional study used data from the second phase of the Birjand Longitudinal Aging Study (BLAS). Sarcopenia was defined using EWGSOP2 criteria. Dietary intake was assessed with a validated food frequency questionnaire, and UPF consumption was categorised into quartiles based on energy contribution (NOVA classification). Logistic and multinomial regression models were applied, adjusting for demographic, behavioural, nutritional and clinical factors. RESULTS: Among 1006 participants (mean age 72.4 ± 6.5 years; 48.2% women), 29.1% had no sarcopenia, 54.4% probable sarcopenia, 8.7% confirmed sarcopenia and 7.7% severe sarcopenia. Higher UPF intake was associated with greater odds of sarcopenia in a dose-dependent manner. In fully adjusted logistic regression models, participants in the third and fourth quartiles of UPF consumption had significantly higher odds of sarcopenia compared with the lowest quartile (Q3: OR = 2.23, 95% CI: 1.17-4.23; P = .014; Q4: OR = 2.50, 95% CI: 1.32-4.74; P = .05). Multinomial analyses further demonstrated that high UPF intake was specifically associated with advanced sarcopenia stages (Q4 vs Q1: Coeff = 2.10, 95% CI: 1.05-4.18; P = .036). CONCLUSION: Higher UPF consumption was independently associated with both the presence and severity of sarcopenia. Reducing UPF intake may help preserve muscle health and lower disability risk in ageing populations.