Obesity is a growing national problem in America. Defined by the CDC as a body mass index (BMI) of 30.0 or higher, obesity is highly correlated with an increased risk of type 2 diabetes. It also can lead to significant increases in healthcare costs. Obesity is particularly prevalent in areas of concentrated poverty. It increases overall economic and health-related burdens on both individuals and the community.
Among its peer cities, Louisville currently ranks 5th in the percent of adults who are 20 and older and are in the obese range — 31.1%.
On this metric, Louisville ranks in the middle tier of its peer group according to a natural breaks algorithm. Cities in green are those that outperform their peers. Cities in yellow represent the middle cluster, and those in red lag behind their peers on this indicator.
In Louisville, the obesity rate among adults 20 and older reached a peak around 2010. Since that point, it has decreased and leveled off, where it now sits just a few tenths of a percentage point above the average rate of its peers. Overall, across peer cities, the average obesity rate has generally increased over the last decade.
Generally, the obesity rate among adults 20 and older has increased over the last decade. That is why even the best performer of the group, Cincinnati, saw an increase in its obesity rate: by about 5 percentage points. Meanwhile, the worst peer performer, Greensboro, saw its adult obesity rate climb by more than 11 percentage points. Louisville’s obesity rate has risen and fallen over the period, but it has ultimately risen less than the rate of its peers.
The adult obesity rate in Louisville among men and women has largely risen and fallen in tandem since 2004. However, in recent years, the rates have diverged. The male obesity rate appears to be on a downward trajectory while the female obesity rate appears to be staying relatively constant.
For each indicator, Greater Louisville Project assigns cities into one of three groups (high-performing, middle-of-the-pack, and low-performing) based on how they compare to other cities. The assignment is based on how cities naturally cluster on that indicator. Sometimes, the differences between cities are very small, and the difference between a city ranked 5th and 6th could simply be a matter of the sampling error that arises from using survey data. Thus, rather than always make a division that declares the top 5 to be the top tier, we use a natural breaks algorithm to look for a cluster of cities that is outperforming the rest, a cluster that is about average, and a cluster that is lagging. This clustering gives us a better indication of where Louisville is thriving and where Louisville has room to learn from cities that are doing better.
Z-scores (or standardization) is a way to combine data with different units of measurement into a single index. The z-score is a measure of how far away a city (or census tract, etc.) is from the average city. In order to be comparable across different units of measurement, the z-score is the distance from the mean measured in standard deviations (e.g. if Louisville has a z-score of 1 it means Louisville is 1 standard deviation above the mean of its peer cities).
Data from the Robert Wood Johnson Foundation's County Health Rankings use z-scores and all z-scores are relative to the mean of Louisville's peer cities. (On the County Health Rankings site z-scores are relative to all the counties in each state - thus z-scores reported by GLP will be different, because we are using a different reference group). The Greater Louisville Project also uses z-scores in our multidimensional poverty index, which compares each census tract to the mean of all census tracts in Louisville.
