WASHINGTON - Americans are exercising more, but that has not done much to slim their waistlines, underscoring the immense challenge confronting health advocates fighting the nation's obesity crisis.
In more than two-thirds of the nation's counties - including some of the most unhealthy - men and women became more physically active over the last decade, according to data published Wednesday.
Women made notable progress nationwide, with the percentage who got sufficient weekly exercise jumping from 46.7 percent to 51.3 percent. The percentage of physically active men ticked up a point to 57.8 percent.
But these improvements have done little to reduce obesity, researchers at the University of Washington's Institute for Health Metrics and Evaluation concluded.
Between 2001 and 2009, obesity rates for men or women fell in just nine counties. National rates climbed throughout the decade, although some recent evidence suggests obesity rates may no longer be rising.
"There has been a lot of progress on physical activity," said Dr. Christopher Murray, lead author of the research, which was published in the journal Population Health Metrics. "To tackle obesity, we need to do this. But we probably also need to do more. … Just counting on physical activity is not going to be the solution."
Today, more than one-third of U.S. adults and about 17 percent of children are obese, according to the federal Centers for Disease Control and Prevention.
Many health experts believe that changing diet may do more to bring those numbers down than increasing exercise.
A separate paper by the institute published Wednesday in the Journal of the American Medical Association identified poor diet as the No. 1 factor contributing to America's poor health compared to other industrialized nations.
Life expectancies in the United States stagnated for women in 1,405 counties and for men in 154 counties between 1985 and 2010, researchers reported.
Murray and others believe that, eventually, the uptick in exercise will likely deliver significant health benefits and may help reverse the decades-long increase in weight.