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A recent major study suggests that medical professionals may need to rethink the traditional way of diagnosing obesity. For many years, body mass index (BMI) has been the go-to method for determining whether someone is overweight or obese.
However, researchers now believe that relying on BMI alone might overlook many individuals who are at a heightened risk for serious health conditions. Researchers from Lund University and AstraZeneca discovered that including waist measurements and body fat percentage offers a more accurate assessment of health risks associated with excess weight.
Their findings were published in eBioMedicine.
With obesity rising to become one of the leading global public health issues, it’s linked to increased chances of developing type 2 diabetes, cardiovascular disease, kidney problems, high blood pressure, and certain types of cancer. While BMI is popular for its simplicity—requiring only height and weight—it doesn’t reveal where fat is stored in the body or how much fat a person truly has.
This is significant because fat accumulated around internal organs and the abdominal area is especially detrimental to health. Over recent years, many scientists have argued that obesity should not be defined solely by BMI. In 2025, experts writing in The Lancet Diabetes & Endocrinology emphasized that BMI on its own isn’t sufficiently reliable for diagnosing obesity. The current study strongly supports this perspective.
The team analyzed data from nearly half a million people in the UK Biobank study—totaling 489,311 participants followed over approximately 13 years. Instead of focusing solely on BMI, they categorized individuals based on body fat percentage and waist circumference, sorting them into five risk levels from low to very high.
They then investigated how these categories correlated with the development of serious health issues over time. During the study period, more than 24,000 experienced major cardiovascular events like heart attacks and strokes. Over 30,000 developed type 2 diabetes, and nearly 15,000 faced chronic kidney disease.
The differences between risk groups were striking. Those with the highest levels of unhealthy body fat had over nine times the risk of developing type 2 diabetes compared to individuals with healthier fat levels. Their risk for chronic kidney disease was doubled, and their likelihood of cardiovascular problems increased by 64%.
One of the most surprising findings was that some individuals with a normal BMI still carried dangerous levels of body fat and poor fat distribution. These individuals wouldn’t typically be considered obese based on standard BMI measurements but still faced significantly higher risks—45% increased risk of cardiovascular disease, 58% higher risk of kidney disease, and more than four times the risk of type 2 diabetes compared to those with healthy fat placement.
The researchers highlight that these results demonstrate why BMI alone might fail to identify many at-risk individuals. Lead researcher Sophie Gunnarsson noted that measuring waist circumference and body fat percentage could enable healthcare providers to better detect people who could benefit from early intervention or preventative measures.
This approach could influence decisions related to lifestyle modifications, medications for obesity, or weight-loss surgery. Rashmi Prasad, another researcher from Lund University, pointed out that the ultimate goal is to move toward more personalized obesity treatment—based on an individual’s actual health risks rather than just a single number.
The study also mirrors a broader shift in how obesity is viewed within the medical field. Increasingly, it’s recognized as a complex disease involving metabolism, inflammation, fat distribution, genetics, and organ health.
While the study predominantly involved participants of European ancestry, the researchers emphasize the importance of future research in more diverse populations. Overall, the evidence suggests that diagnosing obesity may need to become more detailed and individualized. The study’s strengths lie in its large sample size and long follow-up period.
In conclusion, the findings underscore that health risks linked to obesity involve more than just weight. As healthcare evolves, combining measurements like body fat percentage and waist size with BMI may better identify individuals at risk before serious diseases develop.
If you’re interested in weight management, consider reading about how avocados might support weight loss and belly fat reduction, or about how ketogenic diets can cause flu-like symptoms. For additional health insights, check out recent studies linking unhealthy plant-based diets to metabolic syndrome, or learn how certain antioxidants could lower dementia risk.
Source: Lund University.
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