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Why Redefine Obesity?



The third item on the disease definition modification checklist developed by the Guidelines International Network (G-I-N) Preventing Overdiagnosis Working Group published in JAMA Internal Medicine,  pertains to the issue of why modify the disease definition at all?

With obesity being increasingly recognize as a chronic disease, it should be evident to anyone, that the current BMI-based definition of obesity, although simple (or rather simplistic), would label a substantial number of individuals as “diseased”, who may be in rather good health and, therefore, very unlikely to benefit from any obesity treatments (overdiagnosis).

On the other hand, the current BMI-based definition excludes a vast number of people, who may very well have health impairments attributable to abnormal or excess body fat, and may thus benefit from obesity treatments (underdiagnosis).

Although there have been many suggestions for replacing BMI with other anthropometric measures (e.g. waist-to-hip ratio, ponderal index, abdominal sagittal diameter, etc.), none of these measures would guarantee that the individuals identified by such measures, would indeed have health impairments attributable to abnormal or excess weight – their sensitivity and specificity, although perhaps marginally better than BMI in identifying individuals with excess body fat, would still not pass the sniff-test for a reliable diagnostic test of an actual disease.

In fact, given the diversity and heterogeneous nature of adipose tissue, even more precise measures of actual body composition (including sophisticated imaging techniques) would still not be enough to determine whether or not body fat in a given is in fact impairing health and warrants obesity treatment.

In contrast, a definition of obesity that requires the actual demonstration of health impairments (likely) attributable to abnormal or excess body fat, via a clinical assessment, would ensure that obesity is only diagnosed in individuals, who actually have a health problem and would therefore likely benefit from obesity treatments. This may well include individuals below the current BMI cut-off.

Thus, continuing to use BMI (or any other anthropometric measure or more sophisticated estimate of body fat) is simply not an option if we are serious about calling obesity a disease.

@DrSharma
Ottawa, ON

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