Adolescents use dietary supplements marketed for weight loss or muscle building, but these are not recommended by physicians. These products are often ineffective, adulterated, mislabeled, or have unclear dosing recommendations, and consumers have suffered injury and death as a consequence. When Congress passed the Dietary Supplement Health and Education Act, it stripped the Food and Drug Administration of its premarket authority, rendering regulatory controls too weak to adequately protect consumers. State government intervention is thus warranted. This article reviews studies reporting on Americans' use of dietary supplements marketed for weight loss or muscle building, notes the particular dangers these products pose to the youth, and suggests that states can build on their historical enactment of regulatory controls for products with potential health consequences to protect the public and especially young people from unsafe and mislabeled dietary supplements.