As obesity rates rise across the United States, residents in Southern states with lower-than-average incomes per capita are most likely to be dangerously overweight and to suffer related health issues, such as high blood pressure and diabetes, according to a new survey.

The Gallup-Healthways Well-Being Index found seven of the 10 states with the highest obesity rates are in the South. Mississippi has the highest percentage of obese residents, at 35.4 percent, followed closely by West Virginia, Delaware, Louisiana and Arkansas.

On the other hand, residents in the Mountain West are least likely to tip the scales too much. Four of the 10 states with the lowest obesity rates — Montana, Colorado, Nevada and New Mexico — are in the Mountain West, while two other states, California and Hawaii, are in the West.

Montana is the only state in the union in which fewer than 20 percent of the population was obese. The state’s obesity rate stands at 19.6 percent. Colorado’s obesity rate is 20.4 percent, while Nevada’s is 21.1 percent.

Nationwide, the obesity rate has been on a steady rise. The percentage of Americans with a body mass index of greater than 30 has jumped from 25.5 percent in 2008 to 27.1 percent this year, Gallup reported. At least three in 10 residents are obese in 11 states, up from five states that hit the 30 percent mark just last year.

With a wider waistline comes a greater exposure to chronic disease. The percentage of residents in the 10 most obese states who reported being diagnosed with high blood pressure, 35.8 percent, was nearly nine percentage points higher than residents in the 10 least obese states. Residents in the most obese states were much more likely to have high cholesterol, depression and diabetes, as well.

Meanwhile, those who live in the least obese states were more likely to tell Gallup pollsters they ate healthy the day before they were surveyed, that they frequently ate the recommended five daily servings of fruits and vegetables and that they exercised for more than 30 minutes a day.

Those differences lead to higher health-care costs in states with more overweight residents, said James Pope, the chief science officer at Healthways, which commissioned the poll. Pope said the average annual cost of providing care for an obese individual is $1,300 higher than fir someone who is not obese.