Observational evidence has established a relationship between obesity and cancer risk and outcomes. Interventional studies have demonstrated the feasibility and benefits of lifestyle change after cancer diagnosis, and guidelines recommend weight management and regular physical activity in cancer survivors; however, lifestyle interventions are not a routine part of cancer care. The ASCO Research Summit on Advancing Obesity Clinical Trials in Cancer Survivors sought to identify the knowledge gaps that clinical trials addressing energy balance factors in cancer survivors have not answered and to develop a roadmap for the design and implementation of studies with the potential to generate data that could lead to the evidence-based incorporation of weight management and physical activity programs into standard oncology practice. Recommendations highlight the need for large-scale trials evaluating the impact of energy balance interventions on cancer outcomes, as well as the concurrent conduct of studies focused on dissemination and implementation of interventions in diverse populations of cancer survivors, including answering critical questions about the degree of benefit in key subgroups of survivors. Other considerations include the importance of incorporating economic metrics into energy balance intervention trials, the need to establish intermediate biomarkers, and the importance of integrating traditional and nontraditional funding sources. Establishing lifestyle change after cancer diagnosis as a routine part of cancer care will require a multipronged effort to overcome barriers related to study development, funding, and stakeholder engagement. Given the prevalence of obesity and inactivity in cancer survivors in the United States and elsewhere, energy balance interventions hold the potential to reduce cancer morbidity and mortality in millions of patients, and it is essential that we move forward in determining their role in cancer care with the same care and precision used to test pharmacologic and other interventions.