BMI Screening Overlooks Excess Adiposity in Children Without Obesity

Using body mass index (BMI) alone to screen for pediatric obesity accurately identified excess adiposity in nearly all children and adolescents with obesity but failed to detect many cases in those without obesity, according to a research letter published today in JAMA Pediatrics.¹

Although BMI is widely used to classify obesity, the researchers noted that it does not directly measure adiposity, or excess body fat. Therefore, a recent article published in The Lancet recommended incorporating additional measures to confirm adiposity in both adult and pediatric patients with obesity.²

Prior research in adults demonstrated that, based on BMI, 98% of adults with obesity in the US National Health and Nutrition Examination Survey (NHANES) also had excess adiposity when measured by waist circumference and dual-energy x-ray absorptiometry (DXA).³

However, it remained unclear whether screening for obesity using BMI alone might overdiagnose or underdiagnose obesity in children and adolescents.¹ The researchers noted that this is an important issue given the rising rates of pediatric obesity over the past 2 decades.

While body mass index (BMI) accurately identified excess adiposity in nearly all children and adolescents with obesity, it failed to detect many of those without obesity who still had excess body fat. | Image Credit: Vitalii Vodolazskyi - stock.adobe.com

“It is critical to appropriately capture excess adiposity in pediatric populations, particularly those with elevated prevalence of adiposity-related metabolic disease, such as those living on the US-Mexico border,” the authors wrote.

To investigate this question, they analyzed data from the Cameron County Hispanic Cohort (CCHC), a population-based cohort in southern Texas. The study included 183 CCHC participants between the ages of 8 and 17 years, recruited between 2014 and 2023, who underwent both DXA and anthropometric measures, including weight, height, and waist circumference.

The researchers defined excess adiposity among those with obesity as meeting at least one of the following criteria: a waist-height ratio (WHtR) greater than 0.50; severe obesity, defined as a BMI at or above 120% of the 95th percentile; or elevated fat mass index, considered a DXA-based total fat mass divided by height squared at or above the 90th sex- and age-specific percentile from NHANES 1999-2004.

The study estimated the prevalence of obesity with and without confirmed excess adiposity in CCHC participants and compared these findings with those of age- and sex-matched Mexican American, non-Hispanic Black, and non-Hispanic White participants from the NHANES examination years 2013 to 2018.

Among the CCHC participants, 28 (15.3%) were aged 8 to 10 years, 72 (39.3%) were aged 11 to 13 years, and 83 (45.4%) were aged 14 to 17 years. Using BMI alone, 36.1% of CCHC participants were classified as having obesity. By comparison, 30.6% of Mexican American, 23.5% of non-Hispanic Black, and 18.6% of non-Hispanic White NHANES participants were classified as having obesity.

The prevalence of an elevated WHtR was highest among CCHC participants (56.3%), followed by NHANES Mexican American (45.4%), non-Hispanic White (31.7%), and non-Hispanic Black (30.6%) participants. Similarly, the prevalence of an elevated fat mass index was most common among CCHC participants, followed by NHANES Mexican American (21.9%), non-Hispanic White (12.6%), and non-Hispanic Black (12.6%) participants.

Excess adiposity was confirmed in nearly all participants with a BMI at or above the 95th percentile. Specifically, it was confirmed in 98.5% of CCHC participants, as well as 98.2%, 97.1%, and 86.0% of NHANES Mexican American, non-Hispanic White, and non-Hispanic Black participants, respectively. Results were consistent by age among CCHC participants, with excess adiposity present in 100% of participants aged 8 to 10 years, 100% of those aged 11 to 13 years, and 96.3% of those aged 14 to 17 years.

Additionally, DXA and anthropometry measures confirmed excess adiposity in equal numbers overall and across age groups. Importantly, these methods also found excess adiposity in youth without obesity, including 32.5% of CCHC participants, 22.0% of NHANES Mexican American participants, 13.6% of NHANES non-Hispanic Black participants, and 16.8% of NHANES non-Hispanic White participants.

“These youth would be missed in traditional screening by BMI alone, highlighting the importance of incorporating body composition measures into routine clinical care and surveillance,” the authors wrote.

The researchers acknowledged their study’s limitations, including the small sample sizes, which prevented them from addressing pubertal status. Still, they expressed confidence in their findings.

“…our findings emphasize the urgent need for improved early detection strategies in high-risk pediatric populations, given high excess adiposity in youth with and without obesity,” the authors concluded.

References

1. Palmer AB, Lee KH, Roshani R, et al. Prevalence of obesity with confirmed excess adiposity in US children and adolescents. JAMA Pediatr. Published online September 8, 2025. doi:10.1001/jamapediatrics.2025.2991
2. Rubino F, Cummings DE, Eckel RH, et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol. 2025;13(3):221-262. doi:10.1016/S2213-8587(24)00316-4
3. Aryee EK, Zhang S, Selvin E, Fang M. Prevalence of obesity with and without confirmation of excess adiposity among US adults. JAMA. 2025;333(19):1726-1728. doi:10.1001/jama.2025.2704