Associations of Ultra-Processed Food Intake with Body Composition and Blood Pressure Across Sasang Constitution Types: A Prospective Cohort Study

Background/Objectives: High ultra-processed food (UPF) consumption is linked to adverse health outcomes. In Koreans, UPFs contribute approximately one-quarter of daily energy intake. We examined whether the longitudinal associations between UPF intake and changes in body composition, blood pressure (BP), and sleep parameters differ across Sasang constitution types (Taeum, Soeum, and Soyang). Methods: This prospective cohort study included 182 adults aged ≥30 years (baseline: 2015–2017; follow-up: 2019–2021). Dietary intake was assessed only at baseline using a 63-item food frequency questionnaire, and the percentage of total energy intake from UPFs (%UPF) was calculated. Multivariable linear regression models with baseline adjustment were used to evaluate longitudinal changes and interaction effects. Results: In the Soeum type, higher %UPF intake was significantly associated with progressive longitudinal increases in weight (β = 0.27 kg, 95% CI: 0.08 to 0.46), and body mass index (β = 0.09 kg/m2, 95% CI: 0.02 to 0.16), and body fat mass (β = 0.15 kg, 95% CI: 0.00 to 0.30) per 1% increment in %UPF intake, with significant linear dose–response trends across tertiles observed only for weight and BMI (p for trend < 0.05). In the Soyang type, continuous %UPF intake was positively associated with systolic BP (β = 0.36 mmHg, 95% CI: 0.01 to 0.70). No significant longitudinal associations were observed in the Taeum type or for sleep parameters. Overall interaction terms between %UPF intake and constitution types were not statistically significant (all p for interaction > 0.05). Conclusions: In constitution-stratified analyses, higher %UPF intake was longitudinally associated with adverse changes in body composition in the Soeum type and in blood pressure in the Soyang type. Although overall interactions were non-significant, considering constitutional traits alongside dietary assessments may provide exploratory insights into cardiometabolic risk prevention.