This graphic image shows the incidence of diabetes in the USA where an estimated 18 million now have the disease. It is based on county level data. In the darkest parts of the map over 11% have been diagnosed as discussed in this Scientific American article. Given the swathe it cuts across the south, it could perhaps be called a "Grits belt".
It would be very interesting to see a similar graph for Ireland. I don't know if that is possible.