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Monday, January 31, 2011

Health Indicators? Body Mass Index - A Good Start on a Long Journey

Dr. Ali Zentner is a Specialist in Internal Medicine, Obesity and Cardiac Risk Management. She currently practices in British Columbia and Alberta with an office in West Vancouver. Ali is one of the experts on the hit CBC show Village on a Diet and is one of leading medical consultants for CBC's Live Right Now campaign.

I’ve been thinking a lot lately about heath indicators. What is it that makes one measurement superior to another? As a doctor, I am always in search of effective ways in which to measure a patient’s health risk and to convey this risk with accuracy and validity. In a world where the intangible reigns supreme, patients now, more than ever, need some concrete and reliable assessment of their own health risk as a platform to substantiate lifestyle goals and means to achieving these goals.

Let’s be clear.  As a medical community I don’t think we will ever agree on anything, for that matter. In fact, I am a fan of our discord. The variability in our ideas means there is variability in our treatment approaches. Now in an age where chronic disease prevails, medicine needs this kind of diversity more than ever.

And now we come to the topic of obesity in Canada and the body mass index (BMI). In obesity medicine, our three main health indicators are: BMI, waist circumference and co-morbid risks.

BMI has had significant criticism in the past over its usefulness in certain ethno cultural groups and in the overweight population.

Here is my take on the issue.

In patients whose BMI is over 30…. the point is moot. Those patients are obese, regardless of waist circumference and ethnocultural status. I have yet to meet a man or woman with a BMI of 31 who has a “low risk waist”. If you are out there, email me and I will happily print a retraction.

The key here is what is BMI as a determinant of risk? Increased BMI has clearly been demonstrated in a variety of studies as being a marker of increased co-morbid diseases.

A prospective collaborative analysis of BMI versus mortality among 894,576 people in Europe, Asia and North America published in Lancet in 2009 showed an increase in cardiovascular risk factors in patients with body mass indices greater than 25 kg/m2. This study also demonstrated an increased risk in cause specific mortality (namely cardiovascular mortality) in this patient population. The key here, however is patient risk overall.

Make no mistake - I think BMI is a good marker of risk BUT IT DOES NOT STOP THERE.

The key as a physician is for me to use BMI as a screening for other co-morbidities that may exist among patients. Furthermore, it must encourage me to look beyond just the number.

My biggest issue with BMI is that the current numbers clearly are geared towards a Europid population. When it comes to Canadians of non-European descent, the BMI at its current levels for overweight and obese Canadians falls desperately short.

I would argue that we as a country would benefit from a new classification of BMI that was ethnocultural specific. The International Diabetes Association has in fact risk-stratified waist circumferences in accordance with a patient’s ethnocultural background.

This to me is an ideal opportunity for us to widen the spectrum regarding this health indicator.

Overall when it comes to “health indicators”, my position is clear - they are a great place to start the screening process but they are by no means the whole picture.

As with the body mass index, it is a tool for physicians to BEGIN to identify a patient’s risk; a good place to start.

And so the dialogue begins. The dialogue about a patient’s risk profile, lifestyle and physiology and where to begin treatment and management.

If, as they say every journey begins with one step, then BMI may be the beginning of that journey. Where we take things as physicians or patients really is a whole new journey in itself.

Key Words: Health Indicators, Health Promotion


  1. Waist circumference coupled with BMI gives a more accurate prediction of health risk. BMI alone not as predictive.

  2. Dr. Zentner writes, "As a medical community I don’t think we will ever agree on anything, for that matter. In fact, I am a fan of our discord. The variability in our ideas means there is variability in our treatment approaches. Now in an age where chronic disease prevails, medicine needs this kind of diversity more than ever."

    I hope this is not an accurate reflection of what she actually thinks. Some areas of medicine are uninformed by good quality evidence, in which case there is some justification for highly variable approaches to care. But even here, there is an obligation to acquire evidence and at least share experiences to identify the most promising practices as quickly as possible; otherwise a great deal of harm and/or waste occurs. For a great deal of medicine, there is a considerable body of reasonable to high quality evidence to suggest that practices should be thoughtfully standardized. High variability in any industry is the enemy of quality.

    Not only do I not celebrate the notion that doctors will never agree on anything and continue to practice as they see fit irrespective of the evidence; I deplore it. Just as I would deplore it if restaurant inspectors, bridge designers, or auto mechanics were similarly divided. Clinical anarchy that refuses to be informed by the best available evidence is not a sign of admirable professional ferment; it is hubris that in some cases bespeaks negligence.

  3. I think BMI's are pretty much more important to look at than the usual target weight that people have set from looking at magazines. This trending has got to stop.

  4. Over 80 indicators measure the health of the Canadian population and the effectiveness of the health care system. Designed to provide comparable information at the health region and provincial/territorial levels, these data are produced from a wide range of the most recently available sources. Health Indicators are indicators that measure factors associated with the health of Canadians and the health system. This information is provided for Canada’s health regions with a population of at least 50,000, encompassing approximately 98% of the population, as well as provinces and territories.