IntroductionThe weight-adjusted waist index (WWI) serves as an innovative obesity measure, seemingly surpassing body mass index (BMI) and waist circumference (WC) in evaluating lean and fat mass. This study aimed to explore the relationship between WWI and total bone mineral density (BMD) in US adolescents.MethodsThis population-based study investigated adolescents aged 8–19 years with comprehensive WWI and total BMD data from the National Health and Nutrition Examination Survey (NHANES) 2011–2018. WWI was computed by dividing WC by the square root of body weight. Weighted multivariate linear regression and smoothed curve fitting were employed to examine linear and non-linear associations. Threshold effects were determined using a two-part linear regression model. Additionally, subgroup analyses and interaction tests were conducted.ResultsMultivariate linear regression analysis revealed a significant negative association between WWI and total BMD in 6,923 US adolescents aged 8–19 years [β = -0.03, 95% CI: (-0.03, -0.03)]. This negative correlation remained consistent across all subcategories, with the exception of age, encompassing gender,ethnicity, and diabetes status subgroups. Furthermore, a non-linear relationship and saturation effect between WWI and total BMD were identified, with an inflection point at 9.88 cm/√kg.ConclusionsOur research demonstrated a notable negative relationship and saturation effect between WWI and total BMD among US adolescents.