NHS BMI Classifications Wrongly Label Millions as Overweight or Obese
Millions of Britons have been incorrectly categorised as overweight or obese by the NHS, according to a new study. Research indicates that the body mass index (BMI) measure, widely used in healthcare assessments, has led to significant misclassifications across the population.
Study Reveals Widespread Misclassification
The study, conducted by scientists, found that BMI wrongly classified 34% of individuals as obese, while 53% were inaccurately labelled as overweight. This research compared BMI calculations with a gold-standard method that scanned for body fat distribution, muscle mass, bone density, and accounted for age factors.
Currently, the NHS classifies two-thirds of the UK population as overweight or obese based on BMI criteria. If the findings from this Italian study apply to the UK, it suggests approximately five million Britons have been wrongly told they are obese, and over ten million have been incorrectly classified as overweight.
Impact on Healthcare Access
This revelation comes at a critical time, as new evidence shows the NHS is rationing access to life-changing surgeries, such as joint replacements, based on patients' BMI scores. A report by Arthritis UK highlighted that one in five NHS Integrated Care Boards are restricting knee and hip replacement surgeries due to BMI thresholds.
Furthermore, the charity found that 54% of regional NHS commissioning bodies are refusing or delaying operations for patients deemed to have a high BMI. This practice contradicts guidelines set by the National Institute for Care and Excellence (NICE), raising ethical and clinical concerns.
Expert Criticisms and Methodology
Study lead Professor El Ghoch from the University of Verona commented, "Despite the fact that the BMI seems to be reliable in determining body weight status in the normal weight range, over a third of the general population was misclassified, as the current BMI classification appears to inflate the prevalence of underweight, overweight and obesity among the general population."
BMI has long been criticised as a crude measure, with experts citing examples like fit professional rugby players who are categorised as obese due to their muscle mass. The new study, based on 1,350 adults in Italy, used dual-energy X-ray absorptiometry (DXA) scans to reclassify participants.
These scans revealed that 34% of patients classified as obese by BMI were actually overweight, and 53% labelled as overweight were in the wrong category. Among misclassified overweight patients, three-quarters were of normal weight, while the remainder should have been in the obese category.
Consequences for Patients
Deborah Alsina, Chief Executive of Arthritis UK, stated, "This practice is unfair and flies in the face of all guidelines and evidence. People waiting for joint replacement surgery have already spent many months or years with their health and mobility in decline as joint replacement surgery is the final line of treatment."
She added, "Joints in need of replacement are incredibly painful and severely impact the ability of individuals to exercise which can lead to weight gain." This highlights a vicious cycle where pain from untreated conditions can exacerbate weight issues, further complicating BMI-based assessments.
Understanding BMI Calculations
BMI is calculated by dividing an adult's weight in kilograms by their height in metres squared. For example, if someone weighs 70kg and is 1.70m tall, their BMI is computed by squaring the height (1.70 x 1.70 = 2.89) and dividing the weight (70 ÷ 2.89 = 24.22), resulting in 24.2.
Standard BMI thresholds define a healthy weight as 18.5 to 24.9, overweight as 25 to 29.9, and obese as over 30 for adults, typically applying to white backgrounds. Lower thresholds are used for black, Asian, and other minority ethnic groups—with overweight at 23–27.4 and obese over 27.5—due to higher risks of obesity-related conditions at lower weights.
The study's findings underscore the need for a more nuanced approach to weight assessment in healthcare, potentially incorporating advanced scanning technologies to ensure accurate diagnoses and fair access to treatments.
