Nonlinear association of serum copper-zinc ratio with overweight/obesity in children and adolescents

Obesity in children and adolescents has become a serious global public health problem and is closely associated with a range of metabolic diseases. Copper and zinc, as important trace elements, play important roles in energy metabolism, oxidative stress, and lipid metabolism, respectively. An imbalance in the copper-to-zinc ratio may be associated with obesity, but its relationship with obesity in children and adolescents has not been fully explored. The present study explored and revealed the association between the two. This study used data from the National Health and Nutrition Examination Survey (NHANES) between 2011 and 2016, including 1730 children and adolescents aged 6 to 19 years. First, the baseline characteristics of all participants were compared. Subsequently, the association between serum copper-zinc ratio and overweight/obesity was explored by multivariate logistic regression modeling. Next, five subgroup analyses were conducted for gender, age, race, household income, and smoking. Finally, threshold effects were assessed using restricted cubic spline regression analysis and segmented regression modeling. Serum copper-zinc ratio was significantly and positively associated with overweight/obesity in children and adolescents, suggesting a potential relationship (OR = 3.06; 95% CI 2.41-3.92; P < 0.001). Subgroup analyses indicated that the correlations were generally stable and consistent, with significant interactions for race and family income. The prevalence of overweight/obesity increased progressively with increasing copper-zinc ratios. However, this trend was nonlinear, clarifying that a serum copper-zinc ratio of 1.561 was a significant inflection point in this nonlinear relationship. This study explores the association between serum copper-zinc ratio and overweight/obesity in children and adolescents, revealing a nonlinear relationship and its threshold effect. As a measure of oxidative stress and lipid metabolism imbalance, the serum copper-zinc ratio may become a new tool for obesity risk assessment. Given its close association with obesity, the serum copper-zinc ratio should be incorporated into child and adolescent health management for early intervention in the future.