More than 15 percent of the American adult population is physically inactive, according to a new joint survey by the Centers for Disease Control and Prevention and state health departments. People classified as inactive said they had not participated in leisure-time physical activity in the past month: No running or walking for exercise. No gardening. No golf. The most inactive state is Mississippi, with 33 percent of its adult residents labeled inactive. The state with the fewest inactive adults is Colorado, at 17.3 percent. (It is one of only four states — plus the District, at 19.8 percent — with less than 20 percent of their residents classified as inactive. The other three states are Oregon, Utah and Washington.) The South is the region with the most inactive residents — 28 percent — compared with 25.6 percent in the Northeast, 25 percent in the Midwest and 20.5 percent in the West. Besides Mississippi, six other states — Alabama, Arkansas, Kentucky, Louisiana, Oklahoma and Tennessee — had 30 percent or more of their adult residents reporting no leisure-time physical activity. Research has shown that lack of physical activity makes you more likely to develop high blood pressure and high cholesterol and raises your risk for Type 2 diabetes, heart disease, stroke and certain cancers. On the other hand, being active has many benefits, including improving mood, boosting energy, promoting better sleep, controlling or losing weight, building strong bones and muscles and reducing the risk for an array of chronic diseases. It can also help you live longer.