ImportanceUse of nonprescribed weight-loss products in adolescents is a public health concern that is associated with negative physical and psychological consequences. However, the prevalence of nonprescribed weight-loss product use in adolescents is unknown.ObjectiveTo determine the global prevalence of nonprescription weight-loss product use in children and adolescents.Data SourcesFour databases, including MEDLINE, PsycINFO, CINAHL (Cumulative Index of Nursing and Allied Health), and EMBASE, were searched for quantitative studies that reported prevalence data on use of nonprescription weight-loss products with no restrictions on publication date. The search was performed December 1, 2020, and updated March 6, 2023.Study SelectionStudies were included in the meta-analysis if they reported the prevalence of weight-loss product use, were published in English, and included individuals 18 years or younger.Data Extraction and SynthesisData extraction was completed by 2 independent reviewers. Data analysis determined the overall pooled proportion of weight-loss product use in total and during the past week, past 30 days, past year, or lifetime. Inverse variance heterogeneity effect models were used.Main Outcomes and MeasuresThe main outcome measure was the prevalence of nonprescription weight-loss product use in adolescents for all included studies and over the past week, past month, past year, or lifetime. Subgroup analysis included separation of groups by sex, specific weight-loss product types, geographical location, and study publication time.ResultsA total of 90 articles (604 552 unique participants) were included in the meta-analysis. Of these, 50 studies (56%) were from North America. The reported prevalence of weight-loss product use in adolescents was 5.5% (96% CI, 5.5%-5.6%) overall. When identifying use of weight-loss products in the general population, prevalence was 2.0% (95% CI, 1.9%-2.1%) in the past week, 4.4% (95% CI, 4.3%-4.5%) in the past month, 6.2% (95% CI, 6.1%-6.3%) in the past year, and 8.9% (95% CI, 8.6%-9.2%) in their lifetime. Use of weight-loss products was higher among girls than boys.Conclusions and RelevanceThis meta-analysis found that use of weight-loss products occurs at high levels in adolescents, especially girls. These findings suggest that, given the ineffectiveness of these products for weight loss coupled with their harmful long-term health consequences, interventions are required to reduce use of weight-loss products in this group.