Centers for Disease Control and Prevention

Behavioral Risk Factor Surveillance System
This CDC study is the world’s largest, on-going telephone health survey system, tracking health conditions and risk behaviors in the United States yearly since 1984. Overweight/obesity classification by body weight index is one if the risk indicators tracked in this survey. The data is also available by state as Adult Obesity Prevalence Maps.

National Health and Nutrition Examination Survey
This CDC survey is a program of studies designed to assess the health and nutritional status of adults and children in the United States. Weight is one of the indicators tracked in this survey. Navigate to the NCHS Health E-Stats to search for reports on obesity. 

Overweight and Obesity: Data and Statistics
This guide from the CDC provides links to reports on trends in adults and children. Also includes U.S. Obesity Trends by State or Ethnicity, which includes color-coded U.S. maps.

Overweight Prevalence
Faststats from the CDC provide quick links to relevant tables and resources.