TUESDAY, Aug. 25, 2015 (HealthDay News) -- American kids have a harder time controlling their weight than their counterparts to the north, a new U.S. study indicates.
About 17.5 percent of U.S. kids aged 3 to 19 are obese, compared with 13 percent of Canadian children the same age, according to statistics from the U.S. Centers for Disease Control and Prevention.
These findings could open up an exciting new field of obesity research, given that the United States and Canada share a common language and quite a bit of culture, said Peter Katzmarzyk, a professor of pediatric obesity and diabetes at Louisiana State University's Pennington Biomedical Research Center in Baton Rouge.
"There are a number of factors that could be contributing to this difference, but no one's really done a study to uncover what those factors are," said Katzmarzyk. "It gives us an opportunity to explore why these differences are and maybe lead us to some interventions."
Obese children are at risk of becoming obese adults, and therefore more likely than normal-weight kids to develop health problems, such as heart disease and diabetes. More immediately, they are at risk of social problems, high blood pressure and elevated cholesterol, the researchers said in background notes in the report published in the August issue of the CDC's NCHS Data Brief.
In the CDC study, American and Canadian epidemiologists and statisticians collaborated to create an apples-to-apples comparison of childhood obesity in the two countries.
The investigators found that in the late 1970s, the United States and Canada had similar childhood obesity rates -- roughly 5 percent.
Both countries also experienced a steady increase in childhood obesity through the 1980s and 1990s, said study lead author Cynthia Ogden, an epidemiologist at the CDC's National Center for Health Statistics (NCHS).
But for as-yet-unknown reasons, U.S. kids experienced a greater increase. By 2004, about 16.6 percent of U.S. children and teens were obese, compared with 12.4 percent of Canadian kids.
Children in the two countries appear to diverge around the time they enter school, said Kristi King, a clinical instructor of pediatrics at Baylor College of Medicine in Houston.
U.S. and Canadian kids aged 3 to 6 have similar obesity rates. But for children aged 7 to 12, the rates differ dramatically -- 19.2 percent in the United States versus 11.8 percent in Canada, the report said.
"I think this report is going to give us a wake-up call about what we're doing different in that age group that's different from our cousin, Canada," said King, a spokeswoman for the Academy of Nutrition and Dietetics.
While both countries seem very similar, there are countless small distinctions that likely add up to create the observed gap in obesity rates, said Dr. Bruce Lee, director of the Global Obesity Prevention Center at the Johns Hopkins Bloomberg School of Public Health in Baltimore.
"People live and work and play within systems, and they are affected by the environment around them," Lee said. "That all impacts what they eat, how much they move around, how much they exercise. It's important to shift away from blaming the individual and look at what's going on around the individual."
Eating patterns could be one significant difference. King and Katzmarzyk said that earlier research has shown that U.S. families eat out much more often than Canadian families.
"We know that kids who eat at home with their families tend to have lower rates of obesity," King said.
Portion sizes in Canadian restaurants also tend to be smaller than those in the United States, King added. "If families are eating out in the U.S., they're going to be consuming more calories than they would be if they ate out in Canada," she said.
Canadian children also tend to not have televisions in their bedrooms, Katzmarzyk said.
Inactivity connected with TV-watching contributes to obesity, he said. "The American Academy of Pediatrics already recommends that parents remove televisions from children's bedrooms, but I'm not sure how many people actually do it," he added.
Other differences could include availability of healthy foods and city layouts that are designed to promote walking or bicycling, Lee said. It's also possible that Canada does a better job promoting ways to prevent childhood obesity.
"There's a need for more studies," Lee said. "These are things that need to be explored."
For more on childhood obesity, visit the U.S. Centers for Disease Control and Prevention.