WASHINGTON — Adult obesity rates increased in 28 states in 2009, up from 23 states in the previous year, according to “F as in Fat: How Obesity Threatens America’s Future 2010.”

“Obesity is one of the biggest public health challenges the country has ever faced, and troubling disparities exist based on race, ethnicity, region and income,” said Jeff Levi, executive director of the Trust for America’s Health, the organization that produced the report, which is now in its seventh year of publication. “This report shows that the country has taken bold steps to address the obesity crisis in recent years, but the nation’s response has yet to fully match the magnitude of the problem. Millions of Americans still face barriers — like the high cost of healthy foods and lack of access to safe places to be physically active — that make healthy choices challenging.”

The report, which covered all 50 states and the District of Columbia, found 15 states experienced an increase in obesity rates for the second year in a row and 11 states for a third year in a row. Only the District of Columbia experienced a decline in adult obesity rates during 2009.

The rate of adult obesity now exceeds 25% in 38 states, which is an increase from 31 states last year. In addition, the rate of obesity exceeds 30% in 8 states. As recently as 1991, no state had an obesity rate of more than 20%. In 1980, the national average of obese adults was 15%.

For adult obesity rates, Mississippi once again fared the worst, at 33.8%, the sixth consecutive year it has topped the list. Other states exceeding the 30% rate were Alabama (31.6%), Tennessee (31.6%), West Virginia (31.3%), Louisiana (31.2%), Oklahoma (30.6%), Kentucky (30.5%) and Arkansas (30.1%).

Colorado once again was the best, coming in at 19.1%, and remained the only state with a rate below 20%.

Nine of the 10 states with the highest obesity rates were in the South (Michigan was the exception at 29.4%), while northwestern and western states continued to have the lowest obesity rates.

More than one-third of children ages 10 to 17 either are obese (16.4%) or overweight (18.2%), according to the survey. Mississippi was the highest in terms of obese children ages 10 to 17, with a rate of 21.9%. The next closest states were Georgia, at 21.3%, and Kentucky, at 21%. The two states with the lowest childhood obesity rates were Oregon, at 9.6%, and Wyoming, at 10.2%.