Why your BMI might not tell the full story of your health

Health · Published 18 October 2026 Swipe more like this →

In short: Body Mass Index is the global standard for measuring weight, but it is a surrogate marker. While it effectively estimates fatness for most adults, it often fails to account for how fat is distributed across the body—a distinction that can significantly alter your actual health risks.

The World Health Organization (WHO) classifies obesity as a chronic, relapsing disease driven by a complex mix of genetics, neurobiology, and 'obesogenic' environments. To track this, the WHO primarily uses Body Mass Index (BMI), calculated by dividing weight in kilograms by the square of height in meters. For adults, a BMI of 25 or higher is considered overweight, while 30 or higher is classified as obesity. However, because BMI is a surrogate, it does not distinguish between different types of body compositions.

This limitation is particularly notable for individuals like bodybuilders or pregnant women, where BMI may not accurately reflect body fat percentage. To provide a more nuanced picture, clinicians may use additional measurements like waist circumference or the waist-hip ratio to evaluate fat distribution. Emerging methods, such as the Body Volume Index (BVI) being developed by the Mayo Clinic, aim to better account for different body shapes and provide a clearer indication of weight-associated health risks.

The global landscape of obesity is shifting rapidly. In 2022, 1 in 8 people worldwide lived with obesity, with adult obesity more than doubling since 1990. While once viewed as a high-income country issue, it is now a global crisis, particularly in low- and middle-income countries facing a 'double burden' of undernutrition and obesity. Furthermore, some nations, including Japan and China, have even redefined obesity thresholds (e.g., BMI > 25 or > 28, respectively) because their populations may develop negative health consequences at lower BMI levels than Western populations.

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