Adequate nutrition is central to well-being and health and can enhance recovery during illness. Although it is well known that malnutrition, both undernutrition and overnutrition, poses an added challenge for patients with cancer diagnoses, it remains unclear when and how to intervene and if such nutritional interventions improve clinical outcomes. In July 2022, the National Institutes of Health convened a workshop to examine key questions, identify related knowledge gaps, and provide recommendations to advance understanding about the effects of nutritional interventions. Evidence presented at the workshop found substantial heterogeneity among published randomized clinical trials, with a majority rated as low quality and yielding mostly inconsistent results. Other research cited trials in limited populations that showed potential for nutritional interventions to reduce the adverse effects associated with malnutrition in people with cancer. After review of the relevant literature and expert presentations, an independent expert panel recommends baseline screening for malnutrition risk using a validated instrument following cancer diagnosis and repeated screening during and after treatment to monitor nutritional well-being. Those at risk of malnutrition should be referred to registered dietitians for more in-depth nutritional assessment and intervention. The panel emphasizes the need for further rigorous, well-defined nutritional intervention studies to evaluate the effects on symptoms and cancer-specific outcomes as well as effects of intentional weight loss before or during treatment in people with overweight or obesity. Finally, although data on intervention effectiveness are needed first, robust data collection during trials is recommended to assess cost-effectiveness and inform coverage and implementation decisions.