Where do the least obese U.S. residents reside?

Which state has the fittest residents? Make room for the new champ Montana.

The Treasure State had the lowest obesity rates in 2013, according to a new national Gallup poll. Only 19.6 percent of the population was obese, meaning that these people had a body mass index -- a ratio of height to weight -- of 30 and above.

Between 2010 and 2012, Colorado had the lowest obesity rates. In 2013, they dropped to number two.

Nevada, Minnesota and Massachusetts made up the five least obese states.

Across the nation, the Centers for Disease Control and Prevention report that more than one-third of adults are obese. Obesity raises the risk for heart disease, stroke, Type 2 diabetes and several kinds of cancer. The U.S. spent $147 billion in 2008 dollars treating obese patients, about $1,429 more than spent on those who were normal weight.

Obesity was declared a disease by the American Medical Association in June 2013, so people stopped thinking of it as a lifestyle condition.

"While there are a variety of factors that are often correlated with rising obesity rates, such as an unhealthy food environment, poor eating habits, increasing portion sizes, and inactivity, experts agree that the health consequences of obesity are real," Dr. James E. Pope, senior vice president and chief science officer at Healthways, said on the Gallup website.

Where do the unhealthy reside? Out of the 10 states with the highest rates of obesity, seven were in the south.

Mississippi was the fattest state, with 36.4 percent of their population reportedly being obese. West Virginia, Delaware, Louisiana and Arkansas rounded out the top five. All five of those states have been listed among the top 10 most obese since 2008, the first year Gallup tracked the statistics.

With the exception of Montana, at least 20 percent of residents in any of the 50 states were obese. The South and Midwest tended to have the highest rates, while Western and Northeastern areas recorded the lowest numbers.

Not surprisingly, those who lived in the top 10 most obese states were more likely to have had a chronic disease during their life. About 35.8 percent had high blood pressure, 28.2 had high cholesterol, 20.7 percent had depression, 14.3 percent had diabetes, 7.8 percent had cancer and 5.0 percent had experienced a heart attack.

Compare those figures to the 10 least obese states. The residents there only experienced a 26.4 percent incidence of high blood pressure, 23.2 percent incidence of high cholesterol, 20.7 percent incidence of depression, 9.6 percent incidence of diabetes, 7.6 percent incident of cancer and 3.5 percent incidence of heart attack.

In addition, another recent Gallup poll revealed that about two-thirds of people living in the healthy states said they ate healthy all day prior to being surveyed -- and just 6 out of 10 people in the unhealthiest states reported the same behavior. The healthy state residents were also more likely to eat more than five servings of fruits and vegetables during at least four out of seven days, and exercise for at least 30 minutes during at least three days during the prior week.

Lower-income Americans were more likely to say they ate healthy compared to other income levels, but they ate fruits and vegetables less often than Americans with higher incomes.

There was also observed increases in the amount of produce consumed by middle- and upper-income Americans since 2008, but the levels among lower-income individuals stayed about the same. The researchers believe that it may be due to the fact that lower-income Americans aren't getting proper education about healthy eating habits, and believe what they are doing is correct.

The Gallup-Healthways Well-Being Index survey on obesity levels took place on Jan. 2 through Dec. 29, 2013. Around 178,100 adults 18 and older living in the U.S. participated.

The Gallup-Healthways Well-Being Index survey on healthy eating habits took place between Jan. 2 through Dec. 29, 2013. Almost 2 million adults aged 18 or older living in the U.S. and the District of Columbia were surveyed.