WASHINGTON - More than a quarter of Americans self-report that they're obese, and in three states - Alabama, Mississippi and Tennessee - more than 30 percent do, the Centers for Disease Control and Prevention reported Thursday.

Colorado had the lowest reported obesity rate: 18.7 percent.

The 2007 national average of 25.6 percent compares with a 23.9 percent obesity rate in 2005, the CDC said. Actual obesity is likely to be greater, because the figures are based on self-estimated height and weight from telephone health surveys of 350,000 people.

Obesity is defined as a body mass index of 30 or above. It's calculated using height and weight. A 5-foot 9-inch adult who weighs 203 pounds, for example, would have a BMI of 30.

The South reported the highest obesity rate: 27 percent. In the Midwest, it was 25.3 percent, compared with 23.3 percent in the Northeast and 22.1 percent in the West.

Men and women in their 20s were the leanest, according to the CDC. Those in their 50s were most likely to be obese.

Dr. William Dietz, the director of the CDC's Division of Nutrition, Physical Activity and Obesity, offered this prescription: "Eat more fruits and vegetables, engage in more physical activity and reduce the consumption of high-calorie foods and sugar-sweetened beverages."

Obesity rates by state follow. The first number is the self-reported percentage in 2005; the second number is the self-reported percentage in 2007.