New research discounts a common theory on why poor children are more likely to be overweight than children from wealthier families.
Iowa State University researchers say their analysis shows that a lack of food isn't necessarily to blame, although they're not sure why so many children from low-income families are overweight.
Previous research has suggested that poor children weren't getting nutritious food and instead ate junk food, such as hot dogs. Or that children may have eaten well when money was available, but would skip meals when cash was short, a cycle that could slow their metabolism and cause them to gain weight.
By challenging those theories, the researchers hope to encourage more research into the issue. Some studies show that nearly one third of American children ages 10-17 are overweight or obese, and that nearly 40 percent of those kids are from low-income households.
Brenda Lohman, a co-author of the study, said the high number of overweight low-income kids is a public health concern.
"Understanding why the rates are so high .... is needed," she said.
Their findings are reported in February's issue of the Journal of Nutrition.
Donna Matheson, of Stanford Medical School's Prevention Research Center, said the study explores some new elements, but disregards others. She noted that the research only looked at children with weight problems, not those who were underweight.
For the study, the researchers analyzed 1999 data about 1,031 children living in low-income households in Boston, Chicago and San Antonio. They assessed whether the children had enough food for a healthy, active lifestyle, which is called food security by researchers. They looked at the individual child, instead of their entire household as previous studies had done.
The researchers asked the children's mothers whether she had reduced the size of a meal due to lack of food or money, if her child skipped a meal because food wasn't available and if her child went hungry because she couldn't afford more food.
They found that about half of the children in the study were overweight or obese, while only about 8 percent weren't getting enough to eat.
Craig Gundersen, lead author of the study, said children who didn't get enough food weren't more likely to be overweight, even though the two factors often coexisted in the low-income population they studied.
He said the study shows that if the government tries to expand food assistance programs to help children, officials can move forward without worrying about an increase in overweight kids living in poverty.
However, Matheson said she thinks much more research is needed before changes in policy are implemented.
"I don't think we are there yet in terms of saying what really works," she said.
Susan Stewart, an Iowa State sociology professor who was involved in the research, said in a statement that most of the research on childhood obesity comes from the medical community, but there should be a closer look at the family and how factors such as stress affect a child's weight.
"Family life has a lot to do with children's lives, particularly when it comes to overeating and obesity," she said.