Association Between Salt Intake and Body Adiposity in Chinese Population: A Repeated-Measures Cohort Study

Background/Objectives: Several studies have suggested a positive association between salt intake and obesity, yet longitudinal evidence is limited. We aimed to investigate the longitudinal association between salt intake and multiple adiposity indicators. Methods: We used longitudinal data from a cluster-randomized controlled trial conducted in Zhejiang Province, China, including 7372 adults with 12,800 observations. Twenty-four-hour salt intake was estimated using spot urine samples. Adiposity was assessed using body mass index (BMI), body roundness index (BRI), body fat mass, overweight and central obesity. Associations between salt intake and adiposity were evaluated using generalized linear mixed-effects models. Mediation analyses were conducted to quantify the proportion of associations mediated by body fat mass. Results: Mean baseline 24 h salt intake was 9.88 g/d. Compared with participants in the lowest quartile of salt intake (<8.4 g/d), those in the highest quartile (≥11.2 g/d) had higher BMI (difference, 1.14 kg/m²; 95%CI, 1.03-1.25), BRI (0.31, 0.26-0.35), body fat mass (1.88 kg, 1.69-2.07), and higher odds of overweight (OR, 2.82; 95%CI, 2.47-3.22) and central obesity (2.78, 2.42-3.20). Longitudinally, reductions in salt intake (>1 g/d) were associated with decreases in BMI [-0.21 kg/m² (-0.33, -0.09)], BRI [-0.04 (-0.09, 0.00)], and body fat mass [-0.14 kg (-0.36, 0.07)]. Associations were stronger among women and adults aged < 40 years (p-values < 0.05). Body fat mass mediated 56.93%-84.73% of the associations. Conclusions: This study indicates a dose-response association between salt intake and obesity risk, partly mediated by increased body fat mass. The findings suggest that dietary salt may influence cardiovascular risk through adiposity-related pathways.