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Obesity Definition Then And Now

The first 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 how a proposed new definition would differ from the existing definition.

As authors are well aware, the current definition that is widely used to define obesity is based on BMI, a simple anthropometric measure calculated from body height and weight – a great measure of size, not such a great measure of health.

In contrast, the proposed definition of obesity, where obesity is defined as the presence of abnormal or excess fat that impairs health, would require the actual assessment and demonstration of the presence of health impairments attributable to a given subject’s body fat.

Thus, while anyone can currently “diagnose” obesity simply by entering height and weight into a BMI calculator and looking up the value on a BMI chart, the new definition would in fact require a full clinical assessment of an individual’s health. Such an assessment would need to look at both mental and physical health as well as overall well-being for issues that may be directly caused (or aggravated by) the presence of abnormal of excess body fat.

This does in fact bring up the issue of how exactly you would define “abnormal” or “excess” body fat and, even more importantly, how you would establish a relationship between body fat and any health impairments in a given individual.

While these issues would clearly need to be worked out, the face value of this approach should be evident in that it focusses on the issue of actual health impairments rather than an arbitrary BMI cut-off, above which everyone would be considered as having obesity.

This of course raises a number of issues around definition precision and accuracy, which is another item on the checklist and will be discussed in a future post.

Edmonton, AB




  1. Hi Dr. Sharma,

    I like the newly proposed definition of obesity. Taking into account the ways in which abnormal or excess fat impairs health would help individuals qualify for treatments that may not be available to them based on a BMI cutoff alone.

    However, I wonder how the new definition of obesity would impact the rhetoric of obesity. Many people are familiar with the statistics, that in the US over two-thirds of people are overweight and over one-third are obese. If the definition of obesity changes, it could look like we have achieved sudden and dramatic progress in reducing obesity rates across a population, where in fact the progress would only be on paper.

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    • With the new definition, the number of people with obesity may in fact increase quite substantially as a rather large number of individuals in the BMI 25-30 (or less) range, with health problems likely attributable (at least in part) to abnormal or excess weight (e.g. type 2 diabetes, hypertension, sleep apnea, etc.) will be considered to have obesity.

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