New Study Warns BMI Alone May Misclassify Millions with Obesity

A recent study published in the journal Nature has raised concerns about the accuracy of using Body Mass Index (BMI) alone to diagnose obesity. The study, which analyzed health records of over 800,000 individuals in Kenya over a period of up to 15 years, found that relying solely on BMI could miss between 5 and 9 percent of adults who actually have obesity. Conversely, it could also incorrectly classify up to 3 percent of adults as obese.

The researchers, who published their findings in Nature, propose that combining BMI with waist measurements and waist-to-height ratio could provide a more accurate assessment of body fat distribution and its impact on health. Under the new criteria, individuals with a BMI above 40 would be classified as obese outright, while those with lower BMI values would undergo additional checks, such as waist circumference measurements, to determine their obesity status.

The study also highlights the importance of differentiating between "clinical obesity" and "preclinical obesity." Clinical obesity refers to cases where excess fat has already impaired organ function, while preclinical obesity refers to cases where excess fat raises future health risks but has not yet caused health problems. According to the study, only about a quarter to a third of people classified as obese by the new method exhibited clinical obesity, representing roughly 5 to 10 percent of the study population.

Long-term follow-up data showed that 80 to 90 percent of individuals with preclinical obesity did not progress to clinical obesity within ten years, suggesting that excess fat does not inevitably lead to serious disease. This finding has significant implications for how obesity is diagnosed and treated. The study's authors caution, however, that adopting the broader diagnostic framework would require additional measurements and tests, potentially straining health facilities with limited resources.

The World Health Organization estimated that 1.1 billion people lived with obesity in 2024, including about 940 million adults. In Kenya, 12.4 percent of adults were recorded as obese in 2022, with 2.5 percent of children and adolescents affected. These numbers underscore the scale of the diagnostic challenge and the relevance of the study's findings for local health policy.

The study's findings have significant implications for public health policy and practice, particularly in countries like Kenya where obesity is a growing concern. By using a more nuanced approach to diagnosing obesity, healthcare providers may be able to better identify individuals at risk and provide targeted interventions to prevent or treat obesity-related health problems.

The researchers hope that their study will contribute to a better understanding of obesity and its impact on health. By improving the accuracy of obesity diagnoses, healthcare providers can develop more effective treatment strategies and help reduce the burden of obesity-related health problems in Kenya and around the world.

Key points

• The study proposes combining BMI with waist measurements and waist-to-height ratio to improve the accuracy of obesity diagnoses.
• Only about a quarter to a third of people classified as obese by the new method exhibited clinical obesity.
• The World Health Organization estimated that 1.1 billion people lived with obesity in 2024, including about 940 million adults.