Data Limitations and Risks

Data, Trends and Maps provides information about select indicators related to nutrition, physical activity and obesity. While data have been drawn from major data sources, other sources exist that could supplement this information and provide more complete surveillance.

Estimates posted on this Web site may differ from those posted on other CDC and external sites. Differences between estimates can occur because of variations in data definitions, sample inclusion/exclusion criteria and survey and measurement methodology. For example, some data sources, such as the National Health and Nutrition Examination Survey (NHANES), provide information on measured obesity, while the Behavior Risk Factor Surveillance System (BRFSS) relies on self-report for its obesity data. Please refer to footnotes found on the specific indicator pages for detailed information about definitions and inclusion/exclusion criteria or visit the source directly by using the data source link on the indicator summary page.

Statistics in some tables and figures are based on small numbers. These estimates can be unstable, hence inferences should be drawn with caution.