Associations of Serum Zinc and Iron with Systemic Inflammatory Indices in Pediatric Obesity: An Exploratory Cross-Sectional Study

Background/Objectives: Childhood obesity is associated with chronic low-grade systemic inflammation. This exploratory cross-sectional study aimed to evaluate associations between a comprehensive panel of serum micronutrient levels and four systemic inflammatory indices—neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and monocyte-to-lymphocyte ratio (MLR)—in a pediatric cohort, with iron as the primary focus and zinc as a secondary exploratory analysis. Methods: We included 410 children (mean age 7.2 ± 3.8 years; 205 male) attending a tertiary pediatric clinic. Of these, 399 had complete BMI percentile data and were included in obesity-stratified analyses; patients were classified as having obesity (BMI ≥ 95th percentile; n = 56) or not having obesity (n = 343). The remaining 11 children lacked BMI percentile data and were included only in full-cohort analyses. Serum iron, ferritin, folate, zinc, vitamin D, vitamin B12, magnesium, and phosphorus were measured alongside complete blood count parameters. Spearman correlations and multivariable ordinary least squares regression were performed. Benjamini–Hochberg false discovery rate (FDR)-adjusted q-values were computed for all Spearman correlations; all remaining analyses are exploratory and all findings should be interpreted with caution. Results: All four inflammatory indices were significantly higher in children with obesity (SII: 487.1 vs. 332.1, p < 0.001; NLR: 1.30 vs. 1.03, p = 0.001). Low serum iron was more prevalent in the group with obesity (42.9% vs. 27.1%, p = 0.025). In multivariable regression, serum iron was significantly associated with NLR (β = −0.009, 95% CI [−0.012, −0.005], p < 0.001) and SII (β = −3.268, 95% CI [−4.404, −2.132], p < 0.001) after adjustment for age and BMI percentile. In an exploratory analysis restricted to children with obesity and complete data (n = 39), zinc was associated with SII (β = −11.912, 95% CI [−21.836, −1.988], p = 0.025); however, the overall model was non-significant (p = 0.067), zinc showed no association in the full cohort, and—given the small sample and absence of multiple comparison correction—this finding must be considered strictly hypothesis-generating. Conclusions: Systemic inflammatory burden is elevated in children with obesity. Iron shows consistent associations with inflammatory indices independent of age and BMI. Zinc shows a potentially relevant, exploratory association with inflammation, specifically in the subgroup with obesity, warranting replication in adequately powered prospective studies. These findings are consistent with a role for iron status assessment in the clinical evaluation of pediatric obesity and warrant further prospective investigation of zinc-related inflammatory associations.