Obesity is a major public health problem in the United States. Data on measured heights and weights indicates that the prevalence of obesity has significantly increased among the US population over the past 30 years. Data collected from 1999 to 2002 estimates that nearly 1/3 of adults are obese (27.6% of men and 33.2% of women) and one in six children and adolescents is overweight. Increased prevalence of excessive weight is noted among all age, gender and racial/ethnic groups; however, disparities exist. There is a need for further research to better understand why these increases have occurred, why the observed disparities exist and how to reverse these trends.