Purpose <p>This study aimed to investigate the association between one-year changes in body mass index (BMI) and subsequent risk of developing lumbar disc herniation (LDH).</p> Methods <p>A population-based cohort study was conducted using a Japanese administrative claims database, including 4,121,849 individuals with no prior history of LDH who underwent annual health checkups. A multivariable Cox proportional hazards model with restricted cubic splines was used to analyze the dose-response associations between a one-year change in BMI and the risk of development of LDH, adjusting for potential confounders. To assess for effect modification, a subgroup analysis was performed, stratifying participants by baseline BMI categories: &lt;18.5, 18.5 to &lt; 25, 25 to &lt; 30, ≥30.0&#xa0;kg/m².</p> Results <p>During the one-year follow-up, 15,099 individuals developed LDH (1-year risk, 0.38%; 95% confidence interval, 0.37 to 0.39). A restricted spline curve showed that a greater increase in BMI was associated with a higher risk of developing LDH, and this risk increased linearly for BMI changes exceeding 2%. In contrast, the subgroup analysis revealed that among individuals with a BMI ≥ 30&#xa0;kg/m², a one-year increase in BMI was associated with a lower risk of LDH.</p> Conclusion <p>One-year changes in BMI are significantly associated with the risk of developing LDH, but this relationship is dependent on an individual’s baseline BMI. This finding can contribute to the development of preventive strategies such as weight management and exercise therapy for LDH.</p>