The obesity epidemic is not the first major health crisis that the United States has faced. In recent decades, progress has been made against such daunting challenges as tobacco use, infant mortality, and HIV/AIDS. However, obesity may pose the most significant challenge yet because it involves changing approaches to 2 fundamental aspects of daily life: food consumption and physical activity. To have any chance of release from obesity's ever-tightening grip, the nation will require broad-based efforts in every corner of society: homes, schools, community organizations, all levels of government, urban design, transportation, agriculture, the food industry, the media, medical practice, and, without question, biomedical research.