It is well known that childhood obesity puts kids at greater risk for high blood pressure and cholesterol, as well as diabetes and cardiovascular issues. But a large new study has found that obesity can also put children at risk for 20 other surprising health problems, including attention deficit hyperactivity disorder, allergies and ear infections.
"What this information does is to shift the discussion toward the immediate impact of obesity on [children's] health and well-being, and not solely on their 'well-becoming' -- the adults they will become," said study author Neal Halfon, director of the UCLA Center for Healthier Children, Families and Communities.
According to Centers for Disease Control and Prevention estimates, 17 percent of children and adolescents in the U.S. are now obese, a rate that has tripled in a single generation. Public health officials use body mass index, which is a measure of weight relative to height, in order to classify obesity. Children who are in the 85th percentile or higher compared to children of the same age and sex are considered overweight; those with a BMI in the 95th percentile or higher are obese.
In the new study, published in the journal Academic Pediatrics, researchers analyzed data from more than 43,000 children between the ages of 10 and 17 collected in 30-minute phone interviews as part of the 2007 National Survey of Children's Health. Researchers found ties between obesity and 19 indicators of overall health, psychological and social functioning and chronic conditions -- among them ADHD, depression, learning disabilities, asthma and headaches.
The findings, said Dr. Seema Kumar, an assistant professor of pediatrics with the Mayo clinic who researches prevention and treatment of childhood obesity, revealed what researchers call a "dose-response" effect: The more overweight the child, the greater his or her risk of health problems.
"Even when you compared the obese children to the overweight children, the obese children were more likely to have poor quality of health and comorbid conditions," she said. Overall, obese children were almost twice as likely to have multiple health issues.
But while the new research goes a long way in supporting smaller studies that have tied childhood obesity to other health problems, it does not establish causality.
"It's a chicken and egg thing," said Kumar. "Is obesity contributing to these problems, or is that these conditions are predisposing children to obesity?"
"We can presume that some of the associations probably have temporal or causal relationships," echoed Halfon, "but our data cannot make a definitive assertion in that regard."
Some of the co-existing health problems reported by parents may be directly related to obesity, such as diabetes and headache frequency and severity, which have been shown to improve when patients lose weight, the authors wrote. For other problems, like depression, causality could run both ways: Depression might influence eating patterns, but weight gain might also lead to depression.
One final possibility suggested by the study's authors is that obesity and other co-occurring health problems share a common preceding factor. Evidence suggests that ADHD and obesity may both be due to "toxic stress" in a child's early years, which affects both impulse control and insensitivity to leptin, a hormone that helps control appetite.
Notably, the link between obesity and ADHD was only strong in children who were not taking stimulant medications, but not among those taking the drugs. That could mean that children whose ADHD is untreated have other risk factors for obesity, the study's authors wrote, or that stimulants decrease appetite and improve children's impulse control.
With so many questions remaining, Kumar said the message for parents and doctors is to simply be aware that obese children have a greater risk of many health issues, so they can be treated and diagnosed as necessary.
"The bottom line is that this is not just a cosmetic disorder," she said. "It affects every organ in the body. There are physical consequences, and emotional."