Dr. Liping Pan of the Centers for Disease Control and Prevention in Atlanta and colleagues analyzed data from the Pediatric Nutrition Surveillance System, which included almost 50 percent of children eligible for federally funded maternal and child health and nutrition programs.
The analysis involved 26.7 million children ages 2-4 from 30 states and the District of Columbia that consistently reported data from 1998 through 2010.
The 2010 study population was slightly younger and had proportionally more Hispanics and fewer non-Hispanic whites and blacks compared with the 1998 population.
The study, reported in a Research Letter in the Journal of the American Medical Association, found the prevalence of obesity increased from 13.05 percent in 1998 to 15.21 percent in 2003. The prevalence of extreme obesity increased from 1.75 percent in 1998 to 2.22 percent in 2003.
However, the prevalence of obesity decreased slightly to 14.94 percent in 2010; and the prevalence of extreme obesity decreased to 2.07 percent in 2010, the study said.
"To our knowledge, this is the first national study to show that the prevalence of obesity and extreme obesity among young U.S. children may have begun to decline," the authors wrote in the study. "The results of this study indicate modest recent progress of obesity prevention among young children."