Study offers ‘welcome insight’ into updated BMI charts for children
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Key takeaways:
- Last year, the CDC released new BMI-for-age growth charts for children.
- The CDC defines severe obesity as a BMI that is at least 120% of the 95th percentile of BMI-for-age.
Last year, the CDC updated its 22-year-old pediatric BMI-for-age growth charts to add BMIs above the 97th percentile for the first time in order to track severe obesity in children aged 2 to 19 years.
The CDC defines obesity as having a BMI in the 95th percentile or above. Severe obesity is now defined as a BMI equal to 120% or more of the 95th percentile.
A new study published in Pediatrics compared the prevalence of severe obesity among U.S. children and adolescents using the extended percentiles for BMI vs. the new definition of severe obesity.
“We wanted to look at how some of those percentiles from those extended growth charts compared to the cut point for severe obesity in children, which is 120% of the 95th percentile,” Cynthia L. Ogden, PhD, a researcher at the CDC’s National Center for Health Statistics and a co-author of the study, told Healio.
Ogden and colleagues assessed data from the National Health and Nutrition Examination Survey, which collected data on height and weight from 4,749 children and adolescents aged 2 to 19 years from 2017 to March 2020, when the COVID-19 pandemic interrupted the survey.
“What we did is we looked at the percentage of those children who were above the extended 98th percentile — which is based on those new charts we released for children in December with very high BMIs — and compare that to the percentage of children who are above the cutoff point for severe obesity,” Ogden said.
In the sample, 7.7% of children had BMIs equal to or greater than the 98th percentile, compared with 6.7% who had BMIs equal to or greater than 120% of the 95th percentile.
Among children aged 2 to 5 years, the percentage equal or greater to the extended 98th percentile was higher than the percentage equal to or greater than 120% of the 95th percentile.
Children aged 6 to 11 years were more likely to fall into the extended 98th percentile than the original percentile, 8.3% vs. 6.9%. The rates were similar among children aged 12 to 19 years, 8.7% vs. 8.5%.
“This was just a brief methodological report, and there's a figure in the report that actually shows visually how those extended percentiles ... and the 98th extended percentiles are very similar,” Ogden said.
“The bottom line is what we found was that the extended 98th percentile approximates or is very, very similar to 120% of the 95th percentile for older children. The extended 98th equals the definition of severe obesity for older children, but a higher percentage of younger children are above the 98th percentile than above the cut point for severe obesity.”
Ogden and colleagues said clinical studies could determine if the 98th percentile is associated with “comparable levels of health risk across the age span.”
In an accompanying editorial, Sarah E. Barlow, MD, MPH, FAAP, a physician in the department of pediatrics at the University of Texas Southwestern Medical Center, and Sarah E. Hampl, MD, FAAP, a professor of pediatrics at the University of Missouri-Kansas City School of Medicine, said the report provided “welcomed insight” for pediatric health care providers.
“Now that the new extended BMI-for-age growth charts have been released, there is more work to do. Clinicians and researchers can evaluate the health risks associated with different BMI severity levels and the impact of change (improvement or worsening) on health markers,” Barlow and Hampl wrote. “Also important will be evaluation of the meaning of these growth charts for patients, parents, and clinicians, and their utility in communication and decision-making.”
One thing Barlow and Hampl suggested — a point not made explicit in the study, they emphasized — is that the new 98th percentile in the CDC chart “could replace the definition of severe obesity, at least for children aged 6 yeas and above.”
References:
Barlow SE, et al. Pediatrics. 2023;doi: 10.1542/peds.2023-062815.
CDC. 2022 CDC extended BMI-for-age growth charts for children and adolescents with severe obesity. https://www.cdc.gov/nccdphp/dnpao/growthcharts/extended-growth-charts.html. Accessed Aug.30, 2022.
Ogden CL, et al. Pediatrics. 2023;doi:10.1542/peds.2023-062285.
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