Obese eight- and nine-year-olds are more likely to suffer socially and emotionally than their normal-weight peers, a new study finds.
In the study, researchers in Australia checked children's BMI, a measure of height and weight, at ages four and five and then again a few years later. Parents and teachers filled out questionnaires that assessed children's mental health and health-related quality of life.
They found that kids with high BMIs - meaning they were already either overweight or obese - at ages four and five had 15 to 20% greater odds of having problems interacting with their peers, as reported by teachers, when they were eight and nine.
While prior studies have made similar observations about the psychological difficulties faced by obese kids, one question that has vexed researchers is whether obesity leads to social problems, or if it's the other way around - that emotional and other mental health issues such as depression help spur children to become overweight.
Obesity in children
"There have been a number of studies over the past five to 10 years looking at whether or not obesity in young children and adolescents is related to emotional, behavioural and mental health problems," noted Dr Julie Lumeng, an assistant professor in the department of paediatrics and communicable diseases at University of Michigan C.S. Mott Children's Hospital.
"There's been a lot of discussion about which direction that relationship goes in -- does obesity cause children to be unhappy, or is it that unhappy children are more likely to become obese? Many people think it goes in both ways."
According to Lumeng, the new research suggests that children's obesity may have helped prompt their unhappiness, perhaps because kids are getting teased or socially ostracised.
The study, which was led by Michael Gifford Sawyer of Women's and Children's Hospital in Adelaide, is published in the journal Pediatrics.
Obesity is killing children
In the United States, about 17% of children aged two to 19 are obese, according to the US Centers for Disease Control and Prevention. That is much higher than the obesity rate in the sample of nearly 3,400 kids in Australia used in the new study. There, only about 4.5% of boys and 5.2% of girls were obese.
Those differences mean that the effect of obesity on a child's social functioning may be different in the United States than in Australia, Lumeng said.
And despite some difficulties with their peers, obese children were not worse off by other psychological measures, including conduct problems and other mental health issues.
Of course, mental health isn't the only factor to consider in obese kids. Dr Jeffrey Schwimmer, a paediatric gastroenterologist and an associate professor of paediatrics at the University of California, San Diego, said the physical health risks of obesity in childhood can have lifelong consequences. Those include sleep apnoea and fatty liver disease, which can, over time, cause irreversible damage to the liver, diabetes and high blood pressure.
"Obesity at age five is a critical time point in life. It's the age at which most children are entering or in kindergarten, and children who are obese entering kindergarten and who remain obese over those first several years of elementary school are the most likely to end up with the health consequences we see," Schwimmer said.
As for poor social treatment of obese kids, it's not just kids, but other adults and even family members, too, who can be cruel, he added.
"If one looks at what childhood is all about, it's about developing both within our families and our peer groups, and learning both in and out of the school environment," Schwimmer said. "Because obesity is associated with impairment in those things, it can have a long-lasting impact. What I believe this research team was capturing was the change in social standing and the interaction with one's peers and teachers in the school environment that has a greater tendency to be impaired for obese children than for healthy-weight children."
The American Academy of Child & Adolescent Psychiatry has more on childhood obesity.
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