Obesity is growing at a fast pace in the U.S., especially among children. However, a new research suggests that obesity rates may actually be declining in pre-school age children living in low-income families.

Centers for Disease Control and Prevention, says that 17 percent of all children in the U.S., or 12.5 million children and teens, in the country are affected by obesity. Obesity is a risk factor for many health complications that may last a lifetime.

"Obesity and extreme obesity in childhood, which are more prevalent among minority and low-income families, have been associated with other cardiovascular risk factors, increased health care costs, and premature death," wrote Liping Pan of the Centers for Disease Control and Prevention, Atlanta, and colleagues.

The data for the study came from Pediatric Nutrition Surveillance System that includes almost 50 percent of children eligible for federally funded maternal and child health and nutrition programs.

Researchers used data available on 26.7 million children aged 2 through 4 years from 30 states and the District of Columbia. They collected information about demographic and height-weight measurements of each child.

Researchers found that prevalence of obesity rose from 13.05 percent in 1998 to 15.21 in 2003. However, between 2003 and 2010, prevalence of obesity declined to 14.94 percent.

Also, the prevalence of extreme obesity increased from 1.75 percent in 1998 to 2.22 percent in 2003 and then decreased to 2.07 percent in 2010.

"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. "The results of this study indicate modest recent progress of obesity prevention among young children. These findings may have important health implications because of the lifelong health risks of obesity and extreme obesity in early childhood."

The study is published in the Journal of the American Medical Association.