Dr. Julie Lumeng started noticing an alarming pattern while treating children with behavioral problems at an inner-city Boston hospital. When the children -- who recently had become angry or anxious, antisocial, withdrawn or depressed -- returned to the clinic for follow-up visits three to six months later, they often had gained dramatic amounts of weight.
Lumeng, a pediatrician, began to wonder whether the behavioral problems were triggering the weight gains. The opposite had long been thought to be true -- that is, that childhood obesity contributes to behavioral problems because of the bullying, ridicule and poor self-esteem often faced by overweight children.
Lumeng decided to determine whether a correlation could be proven. The result: a national study that concludes that behavioral problems clearly contribute to a child's risk of becoming overweight.
After studying data collected by the Labor Department on 755 children, ages 8 to 11, from 1996 to 1998, Lumeng's team concluded that children with significant behavioral problems, as described by their parents, are nearly three times as likely to be overweight as other children. Moreover, children who develop significant behavioral problems are five times more likely to become overweight in the following two years, regardless of their socioeconomic status.
The findings, published in this month's journal Pediatrics, could affect how the U.S. deals with its epidemic of obesity by focusing more attention on the mental health of children and alerting parents to be aware that weight gain could be a symptom of other problems.
With about 20% of children overweight or obese, U.S. Surgeon General Richard H. Carmona last week launched a campaign aimed at promoting exercise, nutrition and antiobesity programs for young people. The goal is to establish a clearinghouse of programs and information sources for parents, teachers and doctors.
"We are seeing 'Generation Y' grow into 'Generation XL' and this weight gain has long-term health consequences," Carmona told reporters after addressing a convention of the American Academy of Pediatrics.
Lumeng said the results of her study send a bigger message: As we try to prevent obesity, we need to look at the child's mental as well as physical health. "It's not as simple as watching less TV and eating less," she said. "When you have a child that is gaining weight, you have to consider what's at the root of the problem. Behavioral problems predict obesity."
Now a research investigator and pediatrics professor at the University of Michigan, Lumeng performed the study with former colleagues at Boston University, whom she worked with at Boston City Hospital from 2000 until earlier this year.
The study reviewed data taken from children and their mothers collected in the National Longitudinal Survey of Youth, which sends interviewers to participants' homes on a regular basis over several years. It included demographic, weight, behavior, physical and mental health, education and socioeconomic data.
The majority of overweight children in the study did not have a serious behavioral problem, Lumeng said, but there was a significant correlation between the two.
Some of the children Lumeng treated sat in their rooms all day and no longer went out to play. "That's a red flag," she said.
That type of behavioral problem typically is a symptom of something else -- perhaps an issue at school or post-traumatic stress from witnessing some violence.
It also could suggest that the child is genetically predisposed to depression. "The easiest pattern to slip into is to stop playing outside, sit in front of the TV and eat," she said.