In Praise of BMI: Not Perfect But an Exceedingly Useful and Convenient Parameter for Measuring Obesity

One year ago, I had published a review on Obesity  - a 'disease' that is now inflicting almost all societies.  Obesity is the cause of a multitude of ailments; it is not my intention to go over the details again - they are there to read in the review.  Suffice to say that the body mass index (BMI) has proved to be an excellent way to measure obesity and correlates well with observed consequences of obesity; BMI is well understood; easy to define and calculate, and is a great way for the GP to talk to her patients about lifestyle changes etc.- BMI gives a means to the patient to control and monitor her progress.   

I feel that I have to write this blog to critically examine the advice in the recent feature entitled 'It's time to change how we measure obesity'.  The article was also publicised through The Conversation with a title 'Stop measuring obesity with a ruler; we've discovered a far better predictor of health'.
Essentially the article is supposed to be summarizing a study in which a large number, at least 49 , of metabolites were selected for the study of the relationship between obesity and metabolic diseases.  I quote from the paper (my emphasis in red) :

'...However, our study found that metabolite levels did not provide predictive power for future weight changes.  Overall, the metabolome perturbations appear as a consequence of changes in weight as opposed to being a contributing factor.  While BMI correlates well, and to a large extent, with individual health outcomes, it does not have the sensitivity to identify outliers, some of which carry unique health consequences.'

So, the sudy says that BMI is not so good a predictor for outliers - may be less than 1% of the population.

Big deal- BMI has never been claimed to be an exact predictor - it is a useful index for measuring obesity.

I am perturbed by the apparent discrepancy between what is concluded in the research paper and what a senior author has tried to convey through the sensational headlines in the feature published in the World Economic Forum and the Conversation.

I have spent the past 12 years in talking to the community about science matters.  Generally, a non-specialist holds the experts in high regard; and listens and respects the message they are able to give - it is really difficult to translate a research work into language that a layman can understand.  It is our duty to be clear and not mislead the general population.  

BMI is a unique number that is easily understood by the general public.  Obesity is a real scrouge for the society and we need to find ways to control it. It is sad to read a feature article which comes dangerously close to undermining the usefulness of BMI index in the minds of the general public.  Reading the comments in the Conversation,  it seems that some of the readers do believe what the headlines of the features say.

There are better ways to promote one's research work.