This research and policy brief summarizes current research on the factors associated with childhood obesity in the United States, which has more than doubled in the past 30 years. Studies show that although overall childhood obesity rates have plateaued at 17 percent, differences by socioeconomic status appear to be widening. Risk factors for childhood obesity include living in a low-income family; living in a family with high levels of stress; having a mother with an unhealthy weight before or during pregnancy; being part of a racial/ethnic minority group; and living in environments and communities that do not support healthy diets or physical exercise. Obesity during childhood is associated with poorer long-term health, including a higher likelihood of adult obesity and early mortality, as well as adverse social and academic outcomes, such as lower quality of life and a lower likelihood of completing college. Parents can reduce the likelihood of obesity in infancy by using strategies other than food to soothe; developing family routines; promoting healthy sleep patterns; and engaging in appropriate feeding practices. For preschool and school-aged children, school-based interventions have shown promising evidence for reducing obesity. Many promising programs also include a family component. In general, however, less is known about family- and community-based interventions. As such, additional rigorous research is needed to address obesity prevention and intervention outside of school settings. More research is also needed to better understand how particular interventions work for specific subgroups.