WASHINGTON
Americans are exercising more, but that has not done much to slim their waistlines, underscoring the immense challenge confronting doctors and health advocates fighting the nation's obesity crisis.
In more than two-thirds of the nation's counties — including some of the unhealthiest — men and women became more physically active over the last decade, according to data published in the online journal Population Health Metrics. Three-quarters of California's counties saw gains in physical fitness for both men and women.
Women made much more progress than men in raising the level of physical activity. The percentage of California women who got sufficient weekly exercise increased from 50.7 percent to 59.2 percent from 2001 to 2011, while the percentage of physically active men increased from 59.4 percent to 61.3 percent.
But these improvements have done little to reduce obesity, researchers at the University of Washington's Institute for Health Metrics and Evaluation concluded. In California, obesity rates increased in every county between 2001 and 2009. National rates also climbed, although some recent evidence suggests the rates may be leveling off.
"There has been a lot of progress on physical activity," said Christopher Murray, lead author of the research. "But we probably also need to do more. There are still more calories coming in … than calories going out in physical activity."
Today, more than one-third of U.S. adults and about 17 percent of children are obese, according to the Centers for Disease Control and Prevention.
Many health experts say exercise helps prevent disease but that the only way to lose weight is through dietary changes. People need to reduce their insulin levels by drinking less alcohol and eating less sugar, trans fats and cornfed beef and chicken, said Robert Lustig, a neuroendocrinologist and clinical professor at the University of California, San Francisco School of Medicine.