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, authored by Chiara Milanese and colleagues, was published online in Nutrients. The study will also be presented by one of its authors Marwan El Ghoch at the 33rd European Congress on Obesity in Istanbul, Turkey, May 12-15, 2026.

LIMITATIONS: 

The study was limited to White Caucasian participants from a single region in Italy, limiting the generalizability of the findings to other ethnicities and populations. The underweight group had a relatively small number of participants. 

DISCLOSURES:

The authors disclosed having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.