Season of mirth ... and expanding girth.

• Author: Winterfeld, Amy
• Position: STATESTATS

American adults gain an average of one to five pounds during the holidays, and many of them never lose it. The not-so-jolly statistic is a reminder of our nation's uphill battle against obesity.

More than one-third of adults and 17 percent of youth are obese, percentages that remain stubbornly high, according to the Centers for Disease Control and Prevention. In 2013, an estimated 78 million adults and 12 million children fit the definition of obese--roughly 35 pounds overweight for adults, and for children, a body mass index at or above the 95th percentile.

Last year, for the first time, two states reported that more than 35 percent of their adult populations were obese. Another 18 states reported rates at or above 30 percent, and no state had an adult obesity rate of less than 21 percent.

Younger Americans didn't fare much better--obesity rates for 2- to 19-year-olds hovered between 15 percent and 18 percent from 2003 to 2012, the most recent years for which data are available.

For low-income preschoolers, however, a CDC study showed signs of progress; obesity declined for those 2- to 5-year-olds in 19 states from 2008 to 2011.

Because obesity prevalence remains high, however--increasing by roughly 20 percent for adults and 30 percent for children in the past 30 years--the epidemic remains a pressing public health concern, raising...