(CNN) -- Americans are exercising more than in the past, but most are still not working out enough to meet federal guidelines, a new survey shows.
The CDC says more highly educated people were more likely to say they got regular exercise.
From 2001 to 2005, the number of women who said they exercised regularly rose from 43 percent to 46.7 percent; the number of men who said the same thing rose from 46 percent to 49.6 percent, according to a study by the Centers for Disease Control and Prevention.
"Physical activity is increasing among American adults," said lead author and epidemiologist Isa Miles. But she added, "They still have a little work to do."
The study looked at data from the Behavioral Risk Factor Surveillance System, which compared telephone responses from 205,140 people in 2002 with responses from 356,112 in 2005.
Regular physical activity was defined as at least 30 minutes per day of moderate-intensity activity at least five days per week or at least 20 minutes per day of vigorous-intensity activity at least three days per week.
The study found that racial and ethnic differences persist. Among men, non-Latino whites reported exercising the most (52.3 percent), followed by "other race" (45.7 percent), non-Latino blacks (45.3 percent) and Latinos (41.9 percent).
Among women, non-Latina whites were most active (49.6 percent), followed by "other race" women (46.6 percent), Latinas (40.5 percent), and non-Latina blacks (36.1 percent).
People with more education were more likely to say they got regular exercise. Among people who said they had graduated from college, the figures were 54.6 percent for men and 53.3 percent for women, versus slightly more than a third of men and women (37.2 percent and 37.1 percent, respectively) who said they had not graduated high school.
Inactivity has been linked to increased risk for heart disease, high blood pressure, diabetes and obesity.
The authors acknowledged the study has limitations: The data was self-reported, meaning that its accuracy depended on people's ability to recall what happened and to report it truthfully.
In addition, the survey did not include people without land-line phones. More recent surveys included calls to cell phones, a CDC spokeswoman said.
The CDC's Miles said she is among the minority of Americans who said they engage in regular physical activity but added, "You do have to trust me."
She said the study's release on the day before Thanksgiving, when many Americans spend time on a couch in front of a television set, was "purely coincidental." E-mail to a friend