Background: Exposure to environmental pollutants has been associated with obesogenic effects, yet evidence in young children remains sparse. Parabens, widely used as antimicrobial preservatives in personal care products, may disrupt satiety hormones during early life, potentially influencing long-term metabolism and weight regulation. Methods: This cross-sectional study analyzed urinary methyl, ethyl, propyl, and butylparaben (MeP, EtP, PrP, BuP) levels in 4-6-year-old children from the ENVIRONAGE birth cohort using ultra-performance liquid chromatography/tandem mass spectrometry. Plasma satiety hormones (leptin, pancreatic polypeptide, glucagon-like peptide 1, and peptide YY) were measured via (radio-)immunoassays. Associations were assessed in 188 samples using covariate-adjusted linear regression, sex-stratified analysis, and mixture modeling (quantile g-computation and Bayesian kernel machine regression). Additionally, the role of BMI was investigated by partial correlation analysis. Results: As more than 96 % of the BuP measurements were below the LOQ, only the values of MeP, EtP and PrP were used for further statistical analysis. A doubling in PrP was associated with an 5.34 % [95 % Confidence Interval: 1.58 %, 9.23 %] increase in leptin, and BKMR indicated a positive linear association between parabens and leptin. Additional sensitivity analyses were indicative of sex-specific differences in the relationship between parabens, BMI and leptin levels. Conclusions: PrP may increase leptin levels, contributing to obesogenic effects in young children. Given rising childhood metabolic disorders, further longitudinal studies are needed to assess PrP exposure risks in personal care products.

Funding The ENVIRONAGE birth cohort is supported by grants from the Methusalem Fund from the Flemish Government, the Flemish Research Council (FWO G073315 N) and the STOP project of the European Commission (Grant No. 774548H2020). The work of TDR on satiety hormones was also funded by the Flemish Research Council FWO project (FWO G048420N). L.R. was financially supported by the University Research Fund (Bijzonder Onderzoeksfonds Universiteit Hasselt). Acknowledgments We acknowledge the participating mothers and neonates, as well as the staff of the maternity ward, midwives, and the staff of the clinical laboratory of East-Limburg Hospital in Genk.