Follow me on

Should Causality Matter In The Edmonton Obesity Staging System?

One of the questions many readers and colleagues have asked, is whether or not the issue of ‘causality’ should matter in the the context of the Edmonton Obesity Staging System (EOSS).

In other words, should only conditions be counted that are ‘causally’ linked to obesity or is it enough that these conditional are merely more common in people with excess weight.

There are essentially two important but distinct aspects to this question that ultimately relate to how EOSS is to be used in clinical practice.

If the primary purpose of EOSS is to identify patients who would benefit from weight loss, then, yes, it matters whether or not the co-morbidities considered, are ‘causally’ related to obesity and can be reversed or ameliorated by reducing and sustaining a lower body weight.

However, if the primary purpose of EOSS is merely to identify obese patients, who are at high risk and need to be prioritized within the health care system in order to receive the appropriate care for their conditions (irrespective of whether or not this ‘care’ involves weight loss or just better management of their comorbidities), then the question of causality is really irrelevant.

Thus, in the first case, one would only count ‘comorbidities’ that are actually ‘causally’ related to excess weight – an example being sleep apnea. There is ample evidence that weight loss reduces symptoms of sleep apnea (while weight gain makes it worse) and so sleep apnea would count as an important comorbidity that can be addressed by obesity treatment.

In the second case, it does not actually matter if the comorbidity is in any way related to excess weight. All that really matters, is whether this comorbidity is present or not. An e.g. would be depression, which, while not caused by obesity and not likely to improve with weight loss (it may sometimes even get worse), may, when present, help identify obese patients, who do have a higher risk of premature death.

So while in the first example, EOSS would be used to decide who needs to lose weight, in the second example, EOSS simple serves to identify obese people, who are at highest risk of complications and death.

Apart from the second scenario being the real reason that EOSS was developed, it is also a far more practical approach to using EOSS, because for many comorbidities it may be impossible to answer the ‘chicken or egg’ question or even determine if these are simply two different chickens.

In clinical medicine this phenomenon is referred to as ‘phenocopy’, a term used to describe a case where two distinct and unrelated conditions, present clinically with the same symptoms or ‘phenotype’.

In obesity, this is particularly common, because, while many symptoms may be ‘causally’ related to obesity, these same symptoms may just happen to present in an obese individual but have nothing to do with that patient’s excess weight.

For EOSS, this question would not really matter – whether the knee pain is from an accident or from carrying around the excess weight makes no difference – the only thing that matters is that this is a patient with excess weight AND knee pain and therefore, this patient is an obese patient, who is at higher risk for mortality than an obese patient without knee pain.

Remember, bariatric care, as I define it, is not about losing weight but rather about medical care for the bariatric patient. As resources are limited, all I want EOSS to tell me is, who to see first.

Of course there are ‘normal-weight’ people with knee pain, but they are not my problem. There are also ‘normal-weight’ people with high blood pressure, sleep apnea, diabetes and depression – again, they are not my problem.

As someone, who works in an obesity clinic, my job is to assess obese patients and help them the best I can, whether their treatment requires weight loss or not. If EOSS can help me decide, who to see most urgently, then EOSS has done its job.

Of course, further research is needed to determine whether EOSS actually works well in clinical practice (e.g. outside of a speciality centre) and we may perhaps need to simplify and clarify the criteria. But the principle stands: it is simply not enough to look at BMI to decide who needs (urgent) medical attention and who does not.

Edmonton, Alberta


  1. I would love to have a poster or some other lay-oriented display item that I could take with me to my next meeting with my Internist (who serves as my Primary Care Physician) and suggest that he use it to replace the stinking BMI chart on the back of the door in the exam room.

    He doesn’t say things aloud that make people feel bad, but I don’t think he fully appreciates the message that simplistic, stupid BMI chart sends to his patients (especially the women). I know you want to see doctors using your EOSS, for diagnosing, etc., but patients also need to be aware of it, to know that their weight may only be an issue if they develop other conditions (regardless of causality).

    We’ve got the fashion industry making us feel bad enough. We need our doctors to reassure us instead of piling on.

    Post a Reply
  2. I greatly appreciate that both of the papers you published are available for free. I will read them in detail once I have time.

    Also, thank you for clarifying your role. I know you received many comments that may have taken you to task for something that isn’t your role — that the downside of being a blogger AND a doctor who sees actual people in an actual practice.

    I grapple with this, too, in how much to disclose about my work on my blog, and I have the chance to be semi-anonymous on my blog.

    I do think that clarifying the appropriate uses of the EOSS, as the “father” of it, is your role.

    I also agree that when resources are limited, spending money on people who are well but want to lose weight rather than spending money on people who are ill, and need treatment, is not the right thing to do.

    Post a Reply
  3. Hi there,

    RE: “I also agree that when resources are limited, spending money on people who are well but want to lose weight rather than spending money on people who are ill, and need treatment, is not the right thing to do.”

    I partially agree with this statement as well. However, I do believe that more education to the general population to prevent obesity in the first place is warranted. Had I realized the implications on my health of my dieting, overeating, dieting, overeating roller coaster, perhaps I could have stopped or at least slowed down the escalating weight gain earlier on and saved the health care system a lot of dollars down the road? Maybe I would have kept my Staging at stage one instead of stage two?

    So, in my humble opinion, I think we need to have some dollars available for education and prevention of obesity in the first place. A daunting task I know, but with all the research on quick fix dieting being a piece of the obesity problem, I believe money in the prevention area is very necessary. Education on healthy lifestyles before major problems with eating begin is possibly a good place to start. Perhaps weight wise type education models presented in elementary school and high school as part of the curriculum could be a good start? It would probably be best started in Kindergarten. Would presenting this in schools also take some of the monetary burden off of the health care system?

    Just another way of looking at things.

    Thanks for listening,
    Rosemary in Edmonton

    Post a Reply
  4. Hi Dr Sharma,
    Congratulations for your Media Coverage of EOSS ;o)

    I”m working to elaborate an evaluation tool for action plan for Kids.
    I have 2 tenchical question:
    A) could we apply EOSS to kids obesity? (eg. as soon as 6 y?)
    B) did you already know WHAT indicator will you use AND HOW will you evaluate the contribution due to the EOSS to your practice?

    Thank for you’re suggestion. ND

    Post a Reply
  5. Dr. Sharma,

    Children are not not your problem either but more and more of them will be, given North America trends, and it would be nice to see someone playing a proactive role in helping the next generation. Do you have the authority/ability to ask all family doctors and pediatricians in Alberta, with parents permission of course, to complete an EOSS survery on their child patients – you could find out which children are properly at risk now and start that longitudinal study going. Is that feasible? Of course some of the answers would be blank and have to wait until the next checkup, as the majority of these docs have likely never measured waist circumference, for example, but what better way to educate and finally start assisting the truly needy. I wish the government would back it – tax breaks for those who complete the survey – docs and parents alike.

    Post a Reply
  6. EOSS seems very useful to triage scarce medical resources.
    An ER doc would have a similar system. The worst cases get treatment first. The cause of the problem is irrelevant.

    I am interested in prevention.
    To continue my analogy, the ER doc himself would not be expected to enact laws requiring motorcyclists to wear helmets. This is “not his problem”, though it certainly affects who he’ll see in the ER.

    I wonder if you could refer me to sources focusing on prevention of overweight and obesity. Perhaps The Obesity Network has discussions or blogs in this area which would be available to a lay person.

    Post a Reply
  7. Rosemary in Edmonton: You are not alone in dieting yourself up the scale.

    I agree that education is important, but if it only means warning everyone about the “dangers” of obesity (even if you’re at 0 on the EOSS), is not the way to go, especially if the target audience is teenagers and young adults.

    To prevent negative health outcomes, I think the first thing we have to do is acknowledge that we are not all born to be slim, or even to be what people term “average” weight. It follows that striving to lose weight usually becomes a gaining (aka losing) proposition.

    Education should concentrate on the importance of enjoyable physical activity for all (rather than just for those gifted few who were on all the high school teams) and sensible, healthy eating. I know that there are many difference of opinion out there on what healthy eating involves, but I won’t get into that debate here.

    So many people wonder about why we are supposedly in an obesity crisis. I would love to see a study charting the growth of the weight-loss industry and comparing it to the rise in average weight over the last forty years. I suspect that, at least in North America, we have been dieting ourselves fatter every year over the past few decades.

    Post a Reply
  8. Many health problems CAUSE the weight.

    I wrote you on another article, but once I got a normal TSH, the 30lb weight gain per month STOPPED.

    Now is that causation or affect?

    I often wonder how many fat people get fatter due to untreated endocrine illness. Even sleep apnea shuts down hormones in the brain that affect obesity and weight, in other words once you get sleep apnea, and do not go into all the sleep stages your body is not producing hormones needed for a healthy metabolism.

    Post a Reply

Leave a Reply to Fivehundredpoundpeep Cancel reply

Your email address will not be published. Required fields are marked *