A major rethink of how obesity is measured could mean up to 60% more adults are classed as obese, researchers warn.
At present, a BMI between 18.5 and 25 is considered healthy, 25 to 29 is overweight and 30 or above counts as obese – the point where health risks rise sharply.
But 58 global experts argue that BMI alone is too simplistic. They suggest factoring in waist size and the waist-to-height ratio to better reflect unhealthy levels of body fat.
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Harvard University and Massachusetts General Hospital researchers analysed data from more than 300,000 US adults and found that applying these new criteria would boost the number of obese individuals by nearly 60%.
In the UK, where roughly 13 million adults are currently obese, this could mean the total rises to almost 21 million.
Experts described the findings as “important” and warned that the “substantial rise in obesity prevalence” may have “profound financial and public-health implications.”
Under the proposed system, obesity would be defined as a BMI above 30 plus at least one elevated measure, such as waist circumference, waist-to-height ratio or a BMI over 40. Researchers call this BMI-plus-anthropometric obesity.
Adults with a BMI below 30 could also be deemed obese if they meet at least two raised measures, a category labelled anthropometric-only obesity.
In the study, 206,361 adults met the new definition, while only 678 people (0.2%) who were previously obese by BMI were no longer classified as such.
Writing in JAMA Network Open, the researchers said: “The prevalence of obesity increased by 60% when using the new definition compared with the traditional BMI-based one. This rise was entirely driven by inclusion of individuals with ‘anthropometric-only obesity.’”
Despite appearing to have a healthy BMI, these individuals were at significantly higher risk of organ damage and diabetes and were over three times more likely to experience organ dysfunction.
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Nearly 80% of participants aged 70 plus were classed as obese under the new criteria, double the current figure.
“Our findings support inclusion of anthropometric-only obesity within the new obesity definition,” they concluded.
The proposal, first published in Lancet Diabetes & Endocrinology, has been backed by the Royal College of Physicians.
It coincides with new UK government measures to curb obesity, including restrictions on unhealthy food promotions and advertising.
