Obesity rates for each Census Tract in Allegheny County were produced for the study “Developing small-area predictions for smoking and obesity prevalence in the United States." The data is not explicitly based on population surveys or data collection conducted in Allegheny County, but rather estimated using statistical modeling techniques. In this technique, researchers applied the obesity rate of a demographically similar census tract to one in Allegheny County to compute an obesity rate.
For more information, please see: Ortega Hinojosa AM, Davies MM, Jarjour S. et al. Developing small-area predictions for smoking and obesity prevalence in the United States for use in Environmental Public Health Tracking. Environ Res. 2014 Oct; 134:435-52. doi: 10.1016/j.envres.2014.07.029. Epub 2014 Sep 28.
This technique is similar to those used in the 500 Cities project. The 500 Cities project is a collaboration between Centers for Disease Control, the Robert Wood Johnson Foundation, and the CDC Foundation.