Obesity With a Normal BMI? New Obesity Measure Reveals Hidden Burden, Suggests study
USA: A large U.S. study published in the Annals of Internal Medicine suggests that relying solely on body mass index (BMI) may overlook a substantial number of adults with obesity-related health risks. Researchers found that more than one in four adults classified as having a normal BMI met the criteria for “clinical obesity,” a recently proposed diagnostic framework that considers excess body fat and its impact on health rather than weight alone.
The study was led by Hirsh Elhence and colleagues, who examined the national prevalence of clinical obesity using newly proposed criteria from the 2025 Lancet Diabetes & Endocrinology Commission. The framework was developed to address limitations of BMI, which estimates obesity using only height and weight and does not account for body fat distribution or obesity-related organ dysfunction. Under the new approach, obesity assessment incorporates additional measures such as waist circumference, waist-to-hip ratio, and waist-to-height ratio, which better reflect harmful abdominal fat accumulation.
Excess abdominal fat, also known as adipose fat, is associated with chronic inflammation and has been linked to a range of health conditions, including cardiovascular disease, type 2 diabetes, hypertension, liver disease, high cholesterol, and certain cancers. According to the commission, clinical obesity represents a chronic disease state in which excess adiposity contributes to ongoing physical or organ dysfunction. This concept differs from preclinical obesity, where excess fat is present but has not yet resulted in measurable health impairment.
To estimate the burden of clinical obesity in the United States, investigators analyzed data from the National Health and Nutrition Examination Survey (NHANES), a nationally representative health survey. The analysis included 5,642 nonpregnant adults aged 20 years and older who had complete information on BMI and body measurements. Participants had a mean age of approximately 49 years, and just over half were women.
The researchers reported the following findings:
- An adjusted 26.1% of adults with a normal BMI met the criteria for clinical obesity.
- Among adults classified as overweight based on BMI, 50.3% were identified as clinically obese.
- The prevalence of clinical obesity was 65.6% among individuals with class I obesity (BMI 30 to <35).
- Clinical obesity was present in 77.8% of individuals with class II obesity (BMI 35 to <40).
- Among those with class III obesity (BMI ≥40), 85.3% met the criteria for clinical obesity.
- Nearly 78% of U.S. adults showed evidence of excess adiposity when assessed using multiple anthropometric measurements.
- The prevalence of excess adiposity identified through these measurements was substantially higher than estimates based on BMI alone.
The findings suggest that BMI-based screening may underestimate the burden of obesity and obesity-related health risks.
The authors acknowledged that the survey data lacked some of the detailed clinical information needed to fully apply the new diagnostic framework, meaning the true prevalence of clinical obesity may be even higher. They emphasized the need for further research to determine whether adopting the clinical obesity framework improves patient outcomes and helps identify individuals who could benefit from earlier intervention, lifestyle modification, or obesity-specific treatments.
Reference:
https://doi.org/10.7326/ANNALS-25-05287
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