Aug. 30, 2012 -- Only children may be as much as 50% more likely to be overweight than kids who have siblings, a new study suggests.
Even if there is more than one child in the family, the longer the age gaps between siblings, the greater the risk that the first born will be overweight. These findings held even after researchers took into account other factors, including parents' weight and the child's birth weight.
It isn't very clear why only children are more likely to be overweight. Yes, they may play outside less often and have televisions in their bedrooms. But there appears to be something about being an only child all on its own that makes a child more likely to be overweight. The findings appear in Nutrition and Diabetes.
The study included 12,720 children aged 2 to 9 from eight European countries. Only children aged 6 to 9 were 70% more likely to be overweight. By contrast, younger only children were 32% more likely to be overweight. Now researchers are planning a follow-up study of the same families to get a better picture of why only children are more likely to be overweight.
Brian D. Elbel, PhD, reviewed the study for WebMD. He is an assistant professor of population health and medicine at New York University Langone School of Medicine in New York City.
“We should start thinking about family dynamics and what it means for obesity,” he says.
More research is needed to validate the findings and understand why this may occur. "We are not going to say that having a second kid soon after the first is a solution.”
Richard Gallagher, PhD, says that Europeans have smaller families than Americans. He is an associate professor of child and adolescent psychiatry at NYU Langone Medical Center.
“There may be more only children in Europe than children with siblings, which could be driving the study findings,” he says. But, he says, there may be more time for physical play when there are siblings around.
Evan Nadler, MD, co-director of the Children's National Obesity Institute in Washington D.C., says the study suggests an association, but does not connect the dots between being an only child and risk of being overweight.