In 2008, the U.S. federal government issued fully approved physical activity guidelines for the first time. The idea that physical activity impacts health can be traced as far back as Hippocrates, and the science around the linkages between physical activity and health has continuously accumulated. On April 14-15, 2015, the Institute of Medicines Roundtable on Obesity Solutions held a 2-day workshop to explore the state of the science regarding the impact of physical activity in the prevention and treatment of overweight and obesity and to highlight innovative strategies for promoting physical activity across different segments of the population. This report summarizes the presentations and discussions from this workshop.