Problematic muscularity-oriented behaviors, such as excessive weightlifting and muscle-building supplement and substance use (e.g., creatine, steroids), are common among young people, particularly boys and men. Theoretical models of eating disorders, and their constructs, are helpful in conceptualizing a number of risk factors that may increase the likelihood of developing problematic muscularity-oriented behaviors; however, these models lack a clear delineation of the factors that may specifically lead to the initiation and pursuit of these behaviors. This paper provides a brief overview of the theoretical models that have usefully framed research on problematic muscularity-oriented behaviors and the risk factors that been identified through this work. In addition, it identifies gaps related to understanding the factors leading to the initiation and continued or discontinued engagement in these behaviors, and it provides ideas for future research to help fill these gaps. Understanding the ways in which risk factors combine sequentially and interactively, to produce pathways to problematic muscularity-oriented behaviors is crucial for researchers to strengthen theoretical understandings of these behaviors, to inform intervention efforts, and guide policy and practice to decrease their rates among youth.