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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. @DrSharma Edmonton, AB    

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A Checklist For Modifying Disease Defnitions

At the recent European Congress on Obesity in Porto, Portugal, there was much support for calling obesity a chronic progressive relapsing disease. However, there was also much agreement that the current criteria for diagnosing this disease, based on BMI criteria alone, has important limitations in that it may over-diagnose a significant number of individuals at no or very little imminent risk from their body fat and (even more importantly) under-diagnose a substantial number of individuals, who may well stand to benefit from anti-obesity treatments. Thus, as my readers are well aware, I have long called for a redefinition of obesity based on the actual presence of health impairments attributable to abnormal or excess body fat. It is thus timely that JAMA Internal Medicine has just published a seminal article by Jenny Doust and colleagues on behalf of the Guidelines International Network (G-I-N) Preventing Overdiagnosis Working Group, that provides a framework for anyone proposing changes to disease definitions. Using a 5-step process that included (1) a literature review of issues, (2) a draft outline document, (3) a Delphi process of feedback on the list of issues, (4) a 1-day face-to-face meeting, and (5) further refinement, the group developed an 8-item checklist of items to consider when changing disease definitions. The checklist specifically deals with the issues of definition changes, number of people affected, trigger, prognostic ability, disease definition precision and accuracy, potential benefits, potential harms, and the balance between potential harms and benefits. The authors propose that, “…the checklist be piloted and validated by groups developing new guidelines. We anticipate that the use of the checklist will be a first step to guidance and better documentation of definition changes prior to introducing modified disease definitions.” No doubt it would be prudent to consider all of the identified aspects in the checklist, when considering changing the definition of obesity from one based simply on BMI to a more clinical definition, based on actual impairments in health. In coming posts, I will consider each of the proposed checklist items and how they may apply to such a change in the definition of obesity. @DrSharma Edmonton, AB Hat tip to Dr. Marcela Flores for drawing my attention to this paper

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World Obesity Federation Recognises Obesity As a Chronic Relapsing Progressive Disease

Following in the footsteps of other organisations like the American and Canadian Medical Associations, the Obesity Society, the Obesity Medical Association, and the Canadian Obesity Network, this month, the World Obesity Federation put out an official position statement on recognising obesity as a chronic relapsing progressive disease. The position statement, published in Obesity Reviews, outlines the rationale for recognising obesity as a chronic disease and is very much in line with the thinking of the other organisations that have long supported this notion. In an accompanying commentary, Tim Lobstein, the Director of Policy at the World Obesity Federation notes, that recognising obesity as a disease can have the following important benefits for people living with this disease: 1) A medical diagnosis can act to help people to cope with their weight concerns by reducing their internalized stigma or the belief that their problems are self-inflicted and shameful. 2) A classification of obesity as a disease, or disease process, may help to change both the public and professional discourse about blame for the condition, the latter hopefully encouraging greater empathy with patients and raising the patient’s expectations of unbiased care. 3) Recognition of obesity as a disease may have benefits in countries where health service costs are funded from insurance schemes that limit payments for non-disease conditions or risk factors. While all of this is great, and I am truly delighted to see the World Obesity Federation come around to this statement, I do feel that the policy statement seems rather tightly locked into the notion that obesity (or at least most of it) is a disease “caused” primarily by eating too much, with the blame placed squarely on the “toxic obesogenic environment”. Personally, I would rather see obesity as a far more etiologically heterogenous condition, where a wide range of mental, biological and societal factors (e.g. genetics, epigenetics, stress, trauma, lack of sleep, chronic pain, medications, to name a few) can promote weight gain in a given individual. Although these factors may well operate through an overall increase in caloric consumption (or rather, a net increase in energy balance), they, and not the act of overeating per se  must be seen as the underlying “root causes” of obesity. Thus, I tend to see “overeating” (even if promoted by an obesogenic food environment) as a symptom of the underlying drivers rather than the “root cause”. Thus, saying that obesity is primarily caused by “overeating” is… Read More »

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Redefining Obesity Beyond Numbers

As I pointed out in yesterday’s post, there appeared to be broad acceptance for the notion that obesity is a chronic medical disease at the recent 5th Canadian Obesity Summit. In my opening address to the delegates, however, I emphasised that acceptance of obesity as a chronic medical diagnosis requires modification of the definition of obesity to ensure that people diagnosed with this condition do in fact have significant health impairments that warrant them being considered ‘sick’. This is where, the current commonly used ‘definition’ of obesity based on BMI breaks down, as it would ‘misdiagnose’ a significant proportion of Canadians with having a ‘disease’, when in fact they may be perfectly healthy. Moreover, the current BMI-based ‘definition’ of obesity would exclude an even larger group of individuals, who may stand to benefit from anti-obesity treatments as having a BMI that is too low. Let us recall that BMI is really just a measure of size and not a direct measure of actual health. As discussed in a recent editorial published in OBESITY, we have suggested that it would only take a minor (but important) modification of the current WHO definition of obesity to ensure that this label is only applied to people whose health is in fact affected by their body fat. Thus, we have suggested that the current WHO definition, “The presence of abnormal or excess body fat that may impair health.”   be modified to “The presence of abnormal or excess body fat that impairs health.”  This simple change to the wording would have significant implications in that obesity would move from simply being a term used to describe a risk factor (“may impair health“) to being an actual disease (“impairs health“), with all of its consequences for policy, regulators, healthcare systems, research, and clinical practice. Before anyone thinks that this would be far too cumbersome or impractical, let us remind ourselves that such diagnostic approaches are standard practice for a wide range of other diseases that require a clinical encounter, laboratory testing, and/or diagnostic imaging for their diagnosis. In fact, there are very few diseases that can be reliably diagnosed with just a single measure or test. Thus, “…in clinical practice, assessing whether or not abnormal or excess weight is impairing someone’s health should not pose a major diagnostic dilemma. In the vast majority of patients, a few interview questions, a brief physical exam, and a short panel of routine lab tests should readily establish (or… Read More »

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My Miniseries on Obesity As a Disease

Over the past weeks, I have presented a miniseries on the pros and cons of calling obesity a chronic disease. Clearly, I am convinced that the arguments in favour, carry far greater chances of effectively preventing and controlling obesity (defined as abnormal or excess body fat that impairs health) than continuing to describe obesity merely as a matter of ‘lifestyle’ or simply a ‘risk factor’ for other diseases. That said, I would like to acknowledge that the term ‘disease’ is a societal construct (there is, to my knowledge no binding legal or widely accepted scientific definition of what exactly warrants the term ‘disease’). As all societal constructs are subject to change, our definitions of disease are subject to change. Conditions that may once have been deemed a ‘normal’ feature of aging (e.g. type 2 diabetes or dementia) have long risen to the status of ‘diseases’.  This recognition has had profound impact on everything from human rights legislations to health insurance to the emphasis given to these conditions in medical education and practice. People living with obesity deserve no less. Thus, I come down heavily on the ‘utilitarian’ principle of calling obesity a disease. When, calling obesity a ‘disease’ best serves the interests of those affected by the condition, then, by all means, call obesity a ‘disease’ – it is as simple as that. First consequences of the American Medical Association declaring obesity a chronic disease are already evident (see here and here). We can only hope for the same impact of the Canadian Medical Association declaring obesity a disease – the sooner, the better for all Canadians living with obesity. @DrSharma Edmonton, AB

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