Obesity has risen to epidemic levels in the U.S. It causes devastating and costly health problems, reduces life expectancy, and is associated with stigma and discrimination. A multitude of factors likely contribute to obesity, from inherent biological traits that differ between individuals relevant to body weight; to environmental and socioeconomic factors; to behavioral factors--which may have both molecular and environmental influences. Thus, the diverse efforts of many federal agencies and public and private organizations will be valuable in working towards reducing obesity.