About 29 percent of Hispanics and 24 percent of whites are obese, the Centers for Disease Control and Prevention reported.
Racial differences in obesity rates have been reported before, and health officials were not surprised to see larger proportions of blacks tipping the scales.
But the new CDC report is the first to look at the gap on a state-by-state level, finding blacks had much higher obesity rates in 17 states, and had rates about as high or higher than other groups in another two dozen more states.
Health officials believe there are several reasons for the differences. People with lower incomes often have less access to medical care, exercise facilities and more expensive, healthier food. In many places, minorities are disproportionately poor.
But attitudes about weight also are believed to be a factor, said Dr. Liping Pan, a CDC epidemiologist.
"Black and Hispanics are more accepting of high weight," she said, adding that heavy people who are satisfied with their size are not likely to diet or exercise.
Obesity is based on the body mass index, a calculation using height and weight. A 5-foot, 9-inch adult who weighs 203 pounds would have a BMI of 30, which is considered the threshold for obesity.
The data comes from national telephone surveys of hundreds of thousands of Americans in the years 2006 through 2008.