Many Douglas County residents just aren’t feeling all that well. One in five rate their health fair or poor, according to the University of Wisconsin Population Health Institute. The institute, which ranks the health of counties across the nation each year, rated Douglas County second only to Jefferson County as the least healthy county in Oregon in 2012. That’s the bad news. The good news is that a few lifestyle changes — like quitting smoking, eating more vegetables and exercising regularly — could dramatically improve that ranking. What are the 10 biggest health challenges we face? The News-Review asked health …