Public Health Implication of the Edmonton Obesity Staging SystemThursday, August 25, 2011
Continuing our discussion on the implications of the recent publication of our two studies showing that the Edmonton Obesity Staging System (EOSS), which actually measures how ‘sick’ patients are rather than just how ‘big’ patients are, is a better predictor of mortality than BMI, I’d like to briefly discuss a potential implications for public health messaging around obesity and health promotion.
In contrast to what some media commentators have chosen to imply (‘It is now OK to be fat’), EOSS actually takes a very differentiated view of the complexity of the relationship between excess weight and illness.
In fact, one key learning for public health messaging from our EOSS papers, would clearly be to re-evaluate the entire notion of a ‘healthy weight’, an outdated and misleading concept that harks back to the rather simplistic idea of ‘ideal’ weight.
Indeed, we previously criticized the notion of ‘ideal’ weight in an article published in 2009 in SOARD, in which we lamented the use of ‘Excess Weight Loss’ in the bariatric surgical literature.
As we noted in that article:
…ÔÇ£ideal weightÔÇØ is synonymous with the term ÔÇ£desirable weight,ÔÇØ first introduced in 1943 by the Metropolitan Life Insurance Company (MLIC) in their standard height-weight tables for men and women. These tables were determined from actuarial data indicating the lowest mortality risk related to a range of weights for a given height in the studied population. Recognizing that the relationship between mortality and body weight is anything but simple, the MLIC life tables also introduced the concept of frame size, a concept that was hard to understand and implement and was therefore largely ignored. In fact, the current common use of ÔÇ£ideal weightÔÇØ generally refers to the medium frame category, regardless of the patientÔÇÖs actual size or form. Nevertheless, it is important to recognize that for a 170 cm (5ÔÇÖ 7ÔÇØ) woman, depending on her frame size, the MLIC ÔÇ£ideal weightÔÇØ can range from 56 kg for a small frame to 74 kg for a large frame, or a difference of 18 kg. This translates into a body mass index (BMI) range of 19.3ÔÇô25.6 kg/m2, or more than 6 BMI points.”
Thus, not only was this notion of ‘ideal’ weight based on an unrepresentative actuarial sample but there was actually a weight range of about 18 kg (or about 40 lbs) over which a person’s weight for the same height could be considered ‘ideal’.
Our recent EOSS data shows that for some people (albeit a minority at higher BMI levels), this range of ‘ideal’ weight based on mortality can indeed be even larger.
Thus, recognizing that weight (or BMI) is indeed such a crude (some would say irrelevant) measure of ‘health’, the entire concept of ‘healthy weights’ may need to be abandoned in favour of a more differentiated look at the rather complex relationship between health and weight.
At a minimum, public messaging around obesity, may need to make it very clear that ‘health’ can be achieved and maintained across a wide range of weights and that it is probably far more important to focus on health behaviours and other indicators of health than to jump to conclusions about someone’s health based solely on their weight.
Obviously, I fully appreciate that public health messages need to be kept simple but there are certainly arguments to be made that, given the rather loose relationship between health and weight, continuing to promote the notion of ‘healthy weights’ may do more harm than good, as such messaging would simply continue to promote obesity related stereotypes and can potentially set people off on paths of unhealthy weight loss in the firm belief that losing weight is equivalent to improving health.
On the other hand, none of this should distract from the fact that we do have an obesity epidemic and that the vast majority of people with ‘excess’ weight do indeed have relevant comordibities that put them in higher EOSS categories – for these individuals, improving access to evidence-based preventive and treatment resources must be a priority of any healthcare system.
I can certainly see how dealing with this rather complex problem in public health messages and policies will likely lead to a most interesting discussion in the months to come.