The Roundtable on Obesity Solutions of The National Academies of Sciences, Engineering, and Medicine held a virtual workshop on September 16, 2020 titled Using Systems Applications to Inform Obesity Solutions. It explored various systems science approaches (i.e., methodologies and tools) and support structures that could guide future obesity research and action, and featured examples of how these approaches can inform decision making within policy and program areas. Workshop speakers discussed the support structures (e.g., data sources, modeling expertise, training, and partnerships and collaborations) that encourage and engage researchers and decision makers to use systems science approaches to better understand the causes of and solutions to the obesity epidemic. This publication summarizes the presentations and discussions from the workshop.