BMI Misclassifies Many Adults With Obesity

 Have your competent? doctor measure this on you. 

I was at exactly 25 BMI prior to stroke, then gained 30 pounds because my doctor knew nothing and did nothing to get me recovered enough to continue with all the activities that kept me in shape. And told me nothing about slowing metabolism after age 50. Don't know what my DEXA scan is, not concerned

BMI Misclassifies Many Adults With Obesity

TOPLINE:

In an Italian general‑population cohort, BMI misclassified about one third of adults — placing many in incorrect weight categories and modestly overestimating the combined prevalence of overweight and obesity compared with body‑fat percentage measured using DEXA.

METHODOLOGY:

• Despite mounting criticism that BMI fails to accurately capture body fat percentage or distribution, it remains the standard tool for weight‐classification in primary care, health policy, and insurance settings.
• Researchers assessed 1351 White Caucasian participants aged 18-98 years (60% women) from the Italian general population to compare World Health Organization BMI categories with categories based on body fat percentage measured using DEXA.
• Participants were first classified by BMI as having underweight (< 18.5), normal weight (18.5-25.0), overweight (25-30), or obesity (> 30), then reclassified using age‑ and sex‑specific body‑fat percentage thresholds from DEXA.
• The agreement between BMI and DEXA classifications across all weight categories was examined to determine the prevalence of misclassification.

TAKEAWAY:

• According to BMI categories, 1.4% of participants had underweight, 58.3% had normal weight, 26.2% had overweight, and 14.1% had obesity.
• Among participants classified as having obesity by BMI, 34% were reclassified as having overweight by DEXA; among those classified as having overweight by BMI, 53% were reclassified by DEXA — about 75% to normal weight and the remaining 25% to obesity categories.
• In the normal weight BMI group, BMI and DEXA classifications agreed in 78% of participants; the remaining 22% were reclassified by DEXA as having underweight (9.7%), overweight (11.4%), and obesity (0.8%); the greatest disagreement was seen in the underweight BMI group, where 68.4% were reclassified as having normal weight by DEXA.
• The DEXA analysis found the cohort prevalence of overweight and obesity combined to be about 37% overall (23.4% with overweight and 13.2% with obesity) compared with approximately 41% combined by BMI.

IN PRACTICE:

“Public health guidelines in Italy need to be revised to consider combining direct body composition or their surrogate measures such as skinfold measurement or body circumference — such as the waist-to-height ratio — with BMI while assessing weight status in the general population,” the authors wrote. 

SOURCE:

The study was led by Chiara Milanese, University of Verona, Verona, Italy. It was published online in Nutrients and will be presented at the 33rd European Congress on Obesity in Istanbul, Turkey, May 12-15, 2026.