The current body-mass index cut-off point for obesity may not be appropriate for adults aged 40 and older, according to new study findings presented at the European Congress on Obesity in Venice, Italy. Researchers found that a lower BMI threshold of 27 kg/m² may be more accurate in identifying obesity in this age group.
The study, which included 4,800 adults aged 40-80 years, compared the WHO-defined BMI cut-offs for obesity (30 kg/m² and above) with obesity defined by body fat percentage measured using dual x-ray absorptiometry (DXA) scans. The results showed that while around 38% of men and 41% of women were classified as having obesity based on the WHO criteria, a significantly higher proportion—71% of men and 64% of women—were considered to have obesity when assessed according to body fat percentage.
"Our real-world study in a clinical setting in Italy shows that the optimal BMI cut-off point (27 kg/m²) for adults aged over 40 is significantly lower than the widely used one-size-fits-all threshold (30 kg/m²)," said Professor Marwan El Ghoch from the University of Modena and Reggio Emilia in Italy, one of the study's authors. "This new BMI cut off recognizes the physiological differences between middle-aged and older adults and younger populations. It's likely that the changes in body composition across the lifespan, which seem to occur without a meaningful change in body weight, lead to higher adiposity at a lower BMI."
The researchers found that the new BMI cut-off point of 27 kg/m² had a high degree of accuracy in detecting obesity, with a nearly 90% chance of correct classification. However, using the current WHO standard, only 57% of women and around half of men with obesity were correctly identified.
Professor Antonino De Lorenzo, co-author from the University of Rome "Tor Vergata" in Italy, emphasized the potential health implications of these findings: "If we continue to use the WHO standard for obesity screening, we will miss many middle-aged and older adults who are at risk for obesity-related diseases including type 2 diabetes, heart disease, and some cancers. Establishing this new BMI cut-off point in clinical settings and obesity guidelines will be beneficial to the potential health of millions of older adults."
The authors acknowledge some limitations of the study, including its single-center design and the lack of consideration for potential confounders such as dietary habits, physical activity patterns, and sleep health. They call for further larger studies at multiple sites and in other European countries to confirm the results.
They declared having no conflicts of interest.
