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Majority of obese teens already obese before adolescence

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Study investigates patterns of change in childhood obesity over time; data point to need for earlier interventions

BOSTON (Nov. 10, 2014) – Children who are overweight or obese by fifth grade have a high risk of becoming or remaining obese in their teen years, according to a study by researchers from Boston Children's Hospital and elsewhere. Published early online in the journal Pediatrics Nov. 4, the study highlights several factors contributing to that risk, such as watching an excess of television, having an obese parent, having lower household education and having a negative body image.

"We know from prior studies that obesity in children is correlated with their likelihood of being obese when they are older," says study lead author Mark Schuster, MD, PhD, chief of the Division of General Pediatrics at Boston Children's and William Berenberg Professor of Pediatrics at Harvard Medical School. "But the pattern of change over time, of entry to and exit from obesity, hasn't generally been studied."

He adds that several interventions could potentially help reduce an obese child's risk of remaining obese.

"We as clinicians need to do more to educate families and encourage them to have healthier foods at home and especially when they eat outside the home. We also need to encourage them to increase exercise and reduce screen time," says Schuster. "There are also many things we can work towards with schools, such as removing sugar-sweetened beverages, getting physical education back as a priority and improving school meals."

The research team examined data from nearly 4,000 randomly selected children who took part in Healthy Passages, a longitudinal health study of public school children in three metropolitan areas—Birmingham, Alabama; Houston, Texas; and Los Angeles County, California. All of the children had been recruited to the study as fifth-graders between 2004 and 2006.

The researchers re-contacted the children and their families five years later, when most of the children were in tenth grade, to gather additional data on such variables as body mass index and daily habits. They then analyzed factors that affected whether a child became or remained obese between the two time points.

"We studied these children before most had entered adolescence and then again when they were in the middle of their teens," Schuster explained. "This allowed us to avoid confounding changes related to the onset of puberty."

According to the researchers’ analysis:

  • 65 percent of obese fifth-graders remained obese in tenth grade; 23 percent were no longer obese but were still overweight; only 12 percent became normal weight.

  • 87 percent of normal-weight fifth-graders remained at normal weight in tenth grade.

The analysis revealed a number of factors that affected an obese fifth-grader's likelihood of remaining obese in tenth grade, most significantly negative body image and household education. For instance:

  • Obese fifth-graders had a 37 percent chance of losing weight to become overweight if they did not perceive themselves as much heavier than ideal, but only a 26 percent chance if they did.

  • Obese fifth-graders had a 43 percent chance of transitioning to overweight status if they came from households with a college graduate, but only a 33 percent chance if they came from households without a college graduate.

The study also identified several factors that raised an overweight fifth-grader's risk of being obese in tenth grade. Most significant were whether a child watched an excess of television or had a parent who was obese. For example, on average:

  • Overweight fifth-graders had a 21 percent chance of being obese in tenth grade if they watched 30 hours of TV per week and had an obese parent.

  • Those who watched 10 hours per week and had an obese parent had a 6 percent chance.

Additional risk factors for overweight fifth-graders becoming obese included race, education, fast food and soda consumption, and activity level.

Schuster notes that the data highlight the need for doctors and families to address obesity issues when a child is still young.

"Not a lot of children become newly obese in adolescence," he says. "If a child is already obese in fifth grade, she is likely to remain obese, and most children who are obese in tenth grade were already obese before adolescence. We cannot depend on the idea that a child will 'grow out of it' as they get older."

The study was supported by the U.S. Centers for Disease Control and Prevention.

About Boston Children’s Hospital
Boston Children’s Hospital is home to the world’s largest research enterprise based at a pediatric medical center, where its discoveries have benefited both children and adults since1869. More than 1,100 scientists, including seven members of the National Academy of Sciences, 14 members of the Institute of Medicine and 14 members of the Howard Hughes Medical Institute comprise Boston Children’s research community. Founded as a 20-bed hospital for children, Boston Children’s today is a 395-bed comprehensive center for pediatric and adolescent health care. Boston Children’s is also the primary pediatric teaching affiliate of Harvard Medical School. For more information about research and clinical innovation at Boston Children’s Hospital, visit: http://vectorblog.org

To learn more about pediatric health, visit our Thriving blog: http://childrenshospitalblog.org

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Contact:
Meghan Weber
Boston Children's Hospital
617-919-3110 | meghan.weber@childrens.harvard.edu


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