San Antonio tops the charts as the fattest. At 31.1 percent, San Antonio had the highest percentage of obese adults - a category that includes people with a body mass index of 30 or higher, according to a 2001 federal survey.

BMI is a common calculation of weight-to-height ratio.

Gary, Ind., at 28.8 percent, had the second highest percentage of obesity, followed by Jackson, Miss., Fort Wayne, Ind., and Shreveport-Bossier, La.

A BMI of 25 to 29.9 is considered overweight, and San Antonio was No. 2 among cities in both overweight and obese adults. Charleston, W.Va., was No. 1.

The data comes from the Behavioral Risk Factor Surveillance System, a survey conducted by the federal government.

Ali Mokdad, who oversees the survey for the Centers for Disease Control and Prevention, told the San Antonio News-Express that factors such as race and ethnicity, education levels and lifestyle in large part explain the differences between cities.

"We know that the highest increase in obesity has been observed among Hispanics and African Americans," Mokdad said. "It's the makeup of the city, the style of the city, the fast food people like to eat, and the way the cities are defined in terms of access to being able to be physically active."

The 2000 census found that San Antonio has one of the highest percentages of minorities as well as adults without a high school diploma among U.S. cities.