Iron status and dietary iron intake in relation to overweight/obesity in U.S. adults: a nationwide population-based study

Background Evidence on the associations between iron status biomarkers and both overweight/obesity prevalence and body mass index (BMI) is limited. Methods This cross-sectional analysis utilized data from 5,454 participants in the NHANES 2003–2006 and 2017–2020 cycles. Overweight and obesity were defined as BMI ≥ 25 kg/m 2 and ≥30 kg/m 2 , respectively. Weighted multivariable logistic and linear regression models were used to assess associations between iron biomarkers, dietary iron intake, and overweight/obesity risk or BMI. Restricted cubic splines (RCS) were utilized to explore potential non-linear patterns. Furthermore, subgroup analyses stratified by categorical covariates were conducted. Results After adjusting for confounding variables, weighted logistic regression analysis identified reduced odds of overweight/obesity with higher dietary iron intake (OR = 0.98, p = 0.026), serum iron (SI; OR = 0.98, p = 0.004), and transferrin saturation (TSAT; OR = 0.98, p = 0.003). Weighted multivariable linear regression analysis demonstrated inverse associations of dietary iron intake ( β = −0.06, p = 0.045), SI ( β = −0.02, p < 0.001), and TSAT ( β = −0.09, p < 0.001) with BMI. The total iron-binding capacity (TIBC) exhibited a marginal positive association with overweight/obesity risk and BMI. RCS analysis revealed non-linear dose–response relationships between SI, TSAT, TIBC, and overweight/obesity risk. After Bonferroni correction, no significant interaction effects were observed between iron biomarkers and stratified variables. Conclusion Elevated dietary iron intake, serum iron, and TSAT are inversely associated with overweight/obesity risk, highlighting the potential protective role of adequate iron status in preventing obesity.