Metrics Used in the USA to Describe the Food Environment and Its Effects On Obesity: A Systematic Review

Background:  As the obesity epidemic in the United States persists, more researchers work to understand the relationship between the food environment and obesity.  This literature review examines research studies that geospatially analyze the community nutrition environment and its relationship to obesity.  Methods: An extensive literature search on the database MEDLINE was conducted.  Only peer-reviewed studies published in English in the last 10 years were included, ultimately resulting in 51 articles.  Results:  Studies were inconsistent in showing the effect of the community nutrition environment on obesity.  The most commonly measured aspect of the community nutrition environment was the frequency of fast food restaurants, as 44% of 25 articles found a positive association between fast food restaurant frequency and obesity.  Supermarket frequency was inversely related to obesity in 31% of 13 articles that examined this association.  Methods used to identify food stores were also inconsistent. Food store location was measured by varying government sources, private databases, field measurements, and other methods.  Studies also used a variety of methods to define food stores.  Although studies predominately used North American Industry Classification Systems or Standardized Industrial Classification codes (63%), the application of these codes was varied and often unreported.  Discussion: Quality studies have shown a link between the community environment and obesity, but due to heterogeneous methods, it is difficult to directly compare studies and determine why there is such variability.  Further work is needed to develop consistent metrics to measure the community nutrition environment.