Association between urinary glyphosate metabolites and obesity measures in U.S. adults: The mediating role of oxidative stress biomarkers

Glyphosate, a widely used herbicide, has been linked to endocrine and metabolic disruption, but its association with obesity remains unclear. This study examined the relationship between urinary glyphosate levels and obesity metrics, as well as the mediating role of oxidative stress biomarkers. Using NHANES 2013–2018 data from 1,830 adults, weighted logistic and linear regressions were conducted to assess associations between glyphosate concentrations and BMI, waist circumference, and obesity risk. Restricted cubic splines tested dose-response trends, and subgroup interactions were evaluated. Mediation analysis explored the roles of γ-glutamyltransferase (GGT) and serum albumin. Higher urinary glyphosate levels were inversely associated with BMI (β = −1.50; 95% CI: −2.95, −0.05) and waist circumference (β = −3.25; 95% CI: −6.58, 0.08). Compared to the lowest tertile, T3 showed significantly lower BMI and waist circumference, and obesity risk was lower in T2 (OR = 0.90) and T3 (OR = 0.88) (p < 0.05). No nonlinear trends were found, although interactions were observed among alcohol users and low-income groups. GGT and serum albumin partially mediated these associations, with mediation proportions up to 24% and 36%, respectively. These findings suggest that urinary glyphosate levels are inversely associated with obesity indicators, partly through oxidative stress pathways.