Americans are getting fatter and governments are failing to provide solutions to obesity, according to a study of U.S. weight trends.

Thirty-one U.S. states had a higher percentage of dangerously overweight, or obese, adults last year than in the prior year, according to the study by Trust for America's Health. Obesity rates were little changed in 18 states and the District of Columbia. Hawaii was excluded from the analysis.

Being overweight or obese increases a person's risk for developing type 2 diabetes, heart disease and certain cancers. Researchers said the study highlighted weaknesses in federal and state government policies aimed at curbing obesity.

Quick fixes and limited government programs have failed to stem the tide,'' Jeff Levi, the trust's executive director, said in a statement. The fad diet' approach does not work for individuals, and it's not going to work for our nation's obesity crisis either.''

Surveying 26 state-level chronic disease directors, the study said the biggest barriers to addressing obesity are inadequate funding, a lack of political will, and a view that it is more of a personal problem than a public policy issue.

Mississippi is America's fattest state, with 29.5 percent of adults obese and a further 36.4 percent overweight, based on data from 2003 to 2005. Alabama is second with 28.7 percent of adults obese and West Virginia third at 28.6 percent.

Colorado is the slimmest state, with 16.9 percent of adults obese and 36.1 percent overweight. The study showed nine of the 10 fattest states are in the south, while west and northeast states dominate lower rankings.

Mississippi had the highest rate of hypertension and second- highest rate of diabetes, while Colorado ranked last among all states for both conditions.

The study showed obesity rates continue to climb. More than 20 percent of adults are obese in 43 states and in the District of Columbia, while the percentage of adults who are overweight or obese is greater than 60 percent in 28 states.

Researchers use the body mass index, or BMI, to categorize weight. BMI is calculated by dividing a person's weight in pounds by their height in inches squared, then multiplying the total by 703. A BMI of 25 to 29.9 is considered overweight, while a BMI of 30 or above is defined obese.

The Trust for America's Health is a nonprofit group based in Washington. With a grant from the Robert Wood Johnson Foundation, it analyzed state trends using data from the U.S. Centers for Disease Control and Prevention's Behavioral Risk Factor Surveillance System.