Is obesity a disease?
BMI as an indicator of ‘excessive adiposity’ is inherently flawed, particularly in those people with abnormal body habitus, and therefore stumbles as a definition of obesity in some people with excessive muscularity.
Abstract
Shakespeare said that a rose by any other name would smell as sweet. Analogously, obesity as a clinical entity based on its current definition of a BMI>30Kg/m2 remains essentially the same thing, whatever we name it. Unfortunately however, BMI which is calculated from just two basic anthropometric measurements, is seriously limited as a sole diagnostic criterion for obesity. It is accepted that on a population-based epidemiological level, BMI appears to perform well as a measure of adiposity [1]. Although BMI usually also correlates well with adiposity on an individual level, ‘excessive adiposity’ as a concept seems quite subjective. Furthermore, BMI also correlates with muscularity, and therefore stumbles as a definition of obesity in some people with excessive muscularity. Finally, ‘excessive adiposity’ may occur at a BMI <30Kg/m2 in some people with sarcopenia for example. BMI as an indicator of ‘excessive adiposity’ is therefore inherently flawed, particularly in those people with abnormal body habitus. A further limitation of BMI is that it provides no indication of body fat distribution. It is well-established that fat distribution (such as visceral versus subcutaneous gluteal fat) influences risk of metabolic dysfunction and co-morbidity development [2]. Although waist circumference is a useful measure of visceral fat, this measurement does not feature as a diagnostic criterion for obesity based on its current definition.