The Roundtable on Obesity Solutions of the Health and Medicine Division of the National Academies of Sciences, Engineering, and Medicine held a virtual public workshop, Integrating Systems and Sectors Toward Obesity Solutions, on April 6, 2020 (Part I), and June 30, 2020 (Part II). The workshop explored complex systems and contributing factors that can influence obesity, and shared real-life examples of applying systems thinking and systems science approaches to addressing obesity and population health and well-being. In Part I, speakers provided an overview of systems science theories and approaches and their application. In Part II, speakers discussed complex systems in society that have the potential to shape the public’s health and considered opportunities for systems change with regard to obesity solutions. Specifically, the workshop explored how factors such as power dynamics, structural racism, relationships, resources, place-based issues, policy, and political will affect systems that can influence obesity, as well as how these factors can impact communications and cross-sector collaboration to address obesity.