(CNN) — One way health programs today are trying to reduce the growing problem of childhood obesity in the United States is by making parents aware that their child is overweight. The thinking is they can take steps to help their child eat more healthily and exercise more.
But a new study has turned that thinking on its head.
Researchers found that young children were actually more likely to gain weight during childhood if their parents thought they were overweight.
The study monitored more than 3,500 Australian children and found that those who were overweight when they were 4 or 5 years old, and whose parents viewed them as overweight, gained significantly more weight by their 13th birthday. This added gain is in comparison to children who were overweight, but whose parents thought they were actually normal weight or underweight.
"In this case, misperception may be protective," said Angelina R. Sutin, who led the research published Thursday in the journal Pediatrics.
The team determined the body mass index, or BMI, of the children at 4 or 5 years of age and asked one of their parents, in most cases their mother, if they thought their child was underweight, normal weight or overweight. The researchers then measured the child's BMI every other year until they were 13.
Children who were normal weight or underweight also gained more weight at every two-year interval if their parents had mistakenly perceived them as overweight.
Sutin believes the reason behind this could be that parents who thought their children were overweight, regardless of whether they actually were, could have been limiting how much their kids ate and the kids could have rebelled by eating more. Alternatively, these parents may have shamed their children about their weight, which could have led them to overeat or avoid physical activity.
Neither possibility could be tested with the data available from the Australian study, Sutin added.
There is some evidence supporting the second possibility, at least among adolescents and adults. One study found that girls who had been told they were "too fat" by a parent, sibling or peer when they were 10 years old, whether or not they actually were overweight, were more likely to be obese at 19 years. Further research among adults suggests those who label themselves as overweight are more likely to gain weight in subsequent years. But further evidence is needed.
"It is hard to imagine how these mechanisms would play out in the young children in this study," said Dr. William Dietz, chair of the Sumner M. Redstone Global Center for Prevention and Wellness at George Washington University's Milken Institute School of Public Health, who was not involved in the study.
"Parents rarely tell a 5-year-old they have a weight problem," said Dietz, adding that it would be unlikely for a young child to rebel against their parents' efforts to limit calories.
Dietz believes a more likely scenario is that factors other than parental perception could have contributed to weight gain. For example, the group of children who were overweight and correctly categorized as overweight by their parents could have been more severely overweight than the children who were overweight, but not perceived as overweight.
"(The children who are more overweight) could have already been on an increased trajectory of weight gain," Dietz said.
Parents might have been more aware of their child being overweight if they were overweight themselves, and parents who are overweight could be raising children in homes where there is a higher risk of being overweight and obese, with more overeating and less physical exercise, added Dr. Jian Zhang, associate professor of epidemiology at Georgia Southern University's Jiann-Ping Hsu College of Public Health. Zhang has led research examining parents' ability to recognize if their children are overweight, but was not involved in the current research.
Although the study corrected for the parents' BMI and still found the link between parent perception and weight gain, "we cannot rule out the possibility that (it) may explain a large part of the weird observation," Zhang said.
It is also important to know how parents that saw their child as overweight felt about it, and whether they were concerned, Dietz said. For example, parents who are overweight themselves and have experienced poor health outcomes as a result might be more willing to make an effort to reduce their child's weight, he added. The Australian study did not measure parents' attitudes about being overweight or obesity, or their own health.
Recent research in the United States shined an unflattering light on parents and their inability to recognize when their child is overweight, with parents today seeming to be even worse at it than a decade ago. This change could possibly have happened because overweight and obesity among children has become the norm, rather than the exception.
About 32% of children and teenagers, ages 2 to 19, were overweight in 2012 and about 17% were obese in the United States.
Parents in the Australian study also fared poorly. Out of the 3,357 children in the study, 703 were overweight, but only 131 (almost 20%) of them were correctly perceived as overweight by their parents. The remaining 563 were seen as normal weight and nine were seen as underweight.
Given the limitations of the study, it is too soon to conclude that efforts to inform parents about their child's weight are futile and current efforts should continue. One such effort is now in place in 21 states across the United States, where schools assess students' weight, usually by measuring BMI, and share these weight reports with parents.
Some parents have been "furious, and rightly so," about these reports, Dietz said. Parents felt like they were being blamed for their child's weight and ordered to "do something about it," while the school system did not take any responsibility for their role in preventing excessive weight gain in children, he added.
It is important to provide parents with information about their child's weight, and a growing number of pediatricians are accordingly doing BMI screening during wellness visits, Dietz said. However, context makes all the difference. Physicians and public health officials need to do a better job of communicating the health risks of obesity -- which includes diabetes -- rather than just telling people a BMI range to aim for, Dietz said.
Zhang believes it is also important to reduce the stigma about weight among parents, and help them understand that overweight and obesity in children is preventable and reversible, Zhang added.
"As parents, we should foster a pro-health family environment rather than be over-preoccupied by weight watching," Zhang said.
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