On March 2 and 3, 2015, the National Academies of Sciences, Engineering, and Medicine’s Roundtable on Environmental Health Sciences, Research, and Medicine held a workshop to explore the role that chemical exposures may play in the development of obesity. The obesity epidemic that has gripped the United States and much of the developed world for the past several decades has proved remarkably resistant to the various approaches tried by clinicians and public health officials to fight it. This raises the possibility that, in addition to the continued exploration of consumer understanding and behavior, new approaches that go beyond the standard focus on energy intake and expenditure may also be needed to combat the multifactorial problem of obesity.