VENICE, ITALY — Obesity as defined by adiposity measures corresponds to a lower body mass index (BMI) cutoff (≥ 27) in men and women of middle age or older than does the widely used conventional obesity threshold of ≥ 30, shows a study performed in Italy.
Presenting at this year’s European Congress on Obesity (ECO), researchers from the University of Rome Tor Vergata and University of Modena and Reggio Emilia, Italy, and Beirut Arab University, Lebanon, conducted the study to compare the validity of the traditional World Health Organization (WHO) BMI threshold for obesity classification (≥ 30) vs adiposity levels as an alternative measure in middle-aged and older Italians.
Marwan El Ghoch, PhD, a professor in the Department of Biomedical, Metabolic and Neuroscience, University of Modena and Reggio Emilia, presented the findings as a poster (GC4.152). “If you classify obesity with only BMI and without consideration of body composition, then this will not be enough. I believe BMI can be considered as a screening starting point, but we need to understand the body composition of fat and muscle too,” he said.
“We recommend this new cutoff point be applied in clinical settings when screening individuals for obesity in Italy,” El Ghoch asserted.
BMI Limitations Misses Body Composition
If obesity is a chronic disease defined as excessive accumulation of body fat and leading to increased risk for disease, disability, and mortality, then “the identification of obesity based on body fat measurements is the most reliable method,” but he acknowledged that measuring this is not readily available in most clinical settings, and as such, “simple BMI has a place,” Dr. El Ghoch said.
[for example, the shift to more fat and less muscle with age] and it varies by ethnicity,” he pointed out.
This led El Ghoch to ask whether using BMI as a threshold for obesity was suitable for all age groups.
The researchers included 4800 participants of mixed gender aged 40-80 years of age. Based on the WHO’s BMI classification, 1087 people had normal body weight, 1826 had overweight, and 1887 had obesity. The participants were then categorized by adiposity status on the basis of the total body fat percentage as measured by dual-energy x-ray absorptiometry (DXA), and obesity was predicted by statistical analysis.
The analysis found that around 38% of men and 41% of women had a BMI ≥ 30 based on conventional BMI criteria, indicating obesity. However, when assessed according to body fat percentage, around 71% of the men and 64% of the women were determined to have obesity.
Dr. El Ghoch and his colleagues calculated that a lower BMI cutoff of around 27 for obesity in people older than 40 years may be more appropriate than the existing BMI threshold of 30.
The researchers noted some limitations of their work, including that it was a single-center, cross-sectional observational study conducted in one area of Italy. In addition, they did not account for possible confounders, such as dietary habits, and physical activity patterns, and sleep health, all of which can increase the likelihood of obesity and may interact with age-related differences.