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May 27, 2015, 2:57 PM GMT / Updated May 27, 2015, 3:09 PM GMT By Maggie Fox

Americans have become even fatter than before, with nearly 28 percent saying they are clinically obese, a new survey finds.

More than two-thirds of Americans are either overweight or obese, but the new Gallup-Healthways poll shows a record number are tilting the scales from merely overweight into the medically dangerous obese category.

“Mississippi had the highest incidence of obesity in the nation for the second year in a row, at 35.2 percent,” Gallup said in a statement. “Hawaii had the lowest incidence of obesity in 2014, making it the only state where fewer than one in five residents are obese.”

“Mississippi had the highest incidence of obesity in the nation for the second year in a row."

Last year, the group found that about 27 percent of Americans were obese. Their findings fit in with other surveys.

Someone who is 5-foot-5 and weighs 149 pounds has a body mass index of 24, considered a healthy weight. Add a pound and the same person has a BMI of 25 and is considered overweight. At 180 pounds this person has a BMI of 30 and is considered obese.

The National Institutes of Health has a BMI calculator online here.

People who are obese have higher rates of heart disease, diabetes, some cancers, arthritis and Alzheimer’s disease.

But Gallup and Healthways say there are more subtle drawbacks as well.

Even when factoring in education, religion, age and income, obese adults are 29 percent more likely to say they lack purpose in life and nearly 34 percent more likely to suffer financially than non-obese adults, the groups found.

For their survey, Gallup, which specializes in polling, and Healthways, a consultancy firm, surveyed 176,702 adults in all 50 U.S. states and the District of Columbia.

“The national obesity rate in 2014 was the highest that Gallup and Healthways have measured since starting to track this measure in 2008,” Gallup said in a statement.

“In a handful of states, more than a third of the population is obese,” it added. “Obesity-related health problems could drive up healthcare costs and potentially have larger economic implications for states that suffer most.”

Americans say they are trying to lose weight, but are not eating healthy enough or exercising anywhere close to keep them from piling on the pounds, Gallup has found in past surveys.

“The strong relationship between obesity and overall well-being suggests that interventions geared toward encouraging exercise and healthy eating, while important, may not be enough to reverse the upward trend in obesity,” the groups said.

“Obesity-related health problems could drive up healthcare costs."

Governments, nonprofits and health organizations may need to help people in other ways.

“For instance, if residents don't have a strong sense of purpose, struggle financially or lack supportive relationships, it will be much more difficult for them to buy healthy food, exercise regularly and achieve their weight loss goals,” Gallup and Healthways said.

The five slimmest states, with the percentage of population that is obese:

Hawaii: 19 percent

Colorado: 20.3 percent

Montana: 23.5 percent

California: 23.9 percent

Massachusetts: 24 percent

The most obese states: