Precision and Accuracy of Defining Obesity
The fifth 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, deals with issue of precision, accuracy, and reproducibility. Obviously, any definition of obesity that requires clinical assessment and clinical judgement will not have the precision, accuracy, or reproducibility of simply measuring height and weight. Thus, if we define obesity as the presence of abnormal or excess body fat that impairs health, we will necessarily have to deal with the issue of assessing health, which is not something that you can simply measure by stepping on a scale. Rather, because abnormal or excess fat can affect virtually every organ system as well as psycho-social well-being, we are going to be faced with a rather complex system of diagnosing who has obesity and who hasn’t. In fact, as the authors of the checklist point out, “…an appropriate gold standard will rarely be available and therefore, traditional measures of diagnostic test accuracy, such as sensitivity and specificity, will generally not be appropriate.” Both repeatability (agreement in identical conditions) as well as reproducibility (agreement across comparable conditions) may result from biological variability, analytical variability, and clinical judgement. The only way to test the reproducibility and precision will be to evaluate the use of the new definition in clinical practice and ultimately determining whether or not clinicians can reasonably agree on who has the condition and who doesn’t. While this may seem daunting to non-clinicians, let us remember that in clinical practice many diagnoses are dependent on clinical evaluations and clinical judgement, whereby experienced clinicians or specialists may perform better than the novice or the non-specialist (a good example is psychiatry, but there are countless other examples). Moreover, there will always be grey areas in “borderline” cases, where examiners may disagree on the exact result and only time will tell, who is right. Welcome to the messy world of clinical practice. Just because BMI is simpler, more precisely measured, and more reproducible, does not make it a better measure of diagnosing whether or not someone actually has a disease. After all it only makes sense that it will take a complex definition to diagnose a complex disease. @DrSharma Edmonton, AB
Obesity Prognosis
Continuing in my discussion of the disease definition modification checklist developed by the Guidelines International Network (G-I-N) Preventing Overdiagnosis Working Group published in JAMA Internal Medicine, I turn to the fourth item, which deals with issue of prognostic ability of changing the obesity definition? Indeed, as pointed out by the authors of the checklist, “The most important feature of a disease definition is its ability to accurately predict clinically meaningful outcomes.” This, of course is, where BMI fails hands down. As we have demonstrated using several large data sets, the ability of BMI to predict mortality is rather limited with almost no relationship between outcomes and BMIs, at least over a rather wide range of BMI levels. Contrast this to the power of predicting outcomes when using a definition that actually looks at the presence of health impairments, such as the Edmonton Obesity Staging System. When applying this system, which takes into account the impact of excess weight on mental, physical, and functional health, the prognostic power ranges from virtually no risk (Stage 0) to halving your chances of being alive in 20 years (Stage 3). Thus, a definition of obesity that actually considers impairments in health have a far greater prognostic power than simply knowing someone’s BMI. If nothing else, this alone should be a reason to abandon BMI for a more meaningful definition of obesity, that actually considers health and not just size. @DrSharma Edmonton, AB
Impact Of Changing Obesity Definition on Prevalence
The second 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 alter the prevalence of the disease. As indicated in the name of the working group that came up with this checklist, their primary concern is over-diagnosis or “diagnosis-creep”, as often disease modifications tend to increase the number of people covered under said new diagnosis. So what is the implication for prevalence of obesity if we move from a definition based on BMI to one based on an actual impairment of health? Fortunately, we have some data on this, including our own studies on the Edmonton Obesity Staging System, which ranks individuals based on the presence of obesity related impairments in mental, physical, and/or functional health. Based on varying estimates, anywhere between 5-15% of individuals with a BMI over 30 would be considered to be rather healthy with no or minimal health risks. These people would need to be excluded, if obesity was defined as the presence of abnormal or excess body fat that impairs health (they may at best be considered to have “pre-obesity”). This would slightly reduce the number of people considered to have obesity (especially in the BMI 30-35 range). On the other hand, an estimated 40-50% of individuals in the BMI 25-30 range, would actually have significant health problems at least in part attributable to their excess weight, and these individuals may potentially benefit from obesity treatments. Thus, such a change in definition would very substantially increase the number of individuals considered to have obesity. This, of course is something that needs to be carefully considered, as it would clearly have implications for obesity treatment in a significant number of individuals, who at this time would not meet the criteria for obesity management. Let us, however, remember that one would still need to demonstrate significant benefit of treatment in these newly classified individuals. before expanding the indication of existing obesity treatments to these individuals. @DrSharma Edmonton, AB
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 »
Report Card on Access to Obesity Treatment for Adults in Canada 2017: Recommendations
Based on the failing access to obesity care for the overwhelming majority of the 6,000,000 Canadians living with obesity in our publicly funded healthcare systems, the 2017 Report Card on Access To Obesity Treatment For Adults, released the 5th Canadian Obesity Summit, has the following 7 recommendations for Canadian policy makers: Provincial and territorial governments, employers and the health insurance industry should officially adopt the position of the Canadian Medical Association that obesity is a chronic disease and orient their approach/resources accordingly. Provincial and territorial governments should recognize that weight bias and stigma are barriers to helping people with obesity and enshrine rights in provincial/territorial human rights codes, workplace regulations, healthcare systems and education. Employers should recognize and treat obesity as a chronic disease and provide coverage for evidence-based obesity programs and products for their employees through health benefit plans. Provincial and territorial governments should increase training for health professionals on obesity management. Provincial and territorial governments and health authorities should increase the availability of interdisciplinary teams and increase their capacity to provide evidence- based obesity management. Provincial and territorial governments should include anti-obesity medications, weight-management programs with meal replacement and other evidence-based products and programs in their provincial drug benefit plans. Existing Canadian Clinical practice Guidelines for the management and treatment of obesity in adults should be updated to reflect advances in obesity management and treatment in order to support the development of programs and policies of federal, provincial and territorial governments, employers and the health insurance industry. If and when any of the stakeholders adopt these recommendations is anyone’s guess. However, I am certain that since the release of the Report Cards, the relevant governments and other stakeholders are probably taking a closer look at what obesity management resources are currently being provided within their jurisdictions. Given that things can’t really get any worse, there is hope that eventually Canadians living with obesity will have the same access to healthcare for their chronic disease as Canadians living with any other illness. @DrSharma Edmonton, AB
Watch Dr. Sharma in the News!
Listen to Dr. Sharma!
