BMI Calculator – What’s Wrong With It?

weight scaleThe Epi D is about health awareness, real food and lifestyle and not a blog about diet per se but sometimes topics get caught in the cracks.  Take the BMI (Body Mass Index) for example.  I always thought this method of deeming who is overweight or not was more a quick and convenient tool for doctors and not a logical one at that.
Keep in mind that doctors are trained in symptomatic sick-care (note I did not say health-care) usually haven’t a clue about nutrition (not required study in medical school in the US and UK, for example) and may be smokers and overweight themselves.  It is a very rare doctor that motivates her/himself to study nutrition – which by the way is the basis of most alternative health methods.

BMI calculator for women or men is unreliable.

Just the other day I spoke with someone who is tall, athletic for their age (66) and eats copious amounts of vegetables, some fruit and egg or fish a few times a week.  It seems he is ‘overweight’ with a BMI index of 27.  I did not notice any excess curves on him anywhere and we both laughed it off.

It is not the first time.  I know of another example of a young, active woman very much into outdoors sports and a serious hiker who had to have a routine check up with a new doctor.  While waiting, the nurse took her history and did the usuals such as checking the BMI.  She was told she had to lose weight because her BMI index is high and was pushed a generic diet plan.

The nurse showed no reaction when the woman explained her hobbies and lifestyle (since the nurse did not ask).  This young women is of average height but has muscular legs and is in general a very strong, but not ‘muscular’ young woman.  The woman spoke to the doctor and gave him back his diet plan which she considered not healthy enough for her lifestyle.  She certainly did not need a ‘diet plan’.  Did I mention she is also a yoga instructor?

In her mind, the doctor lost credibility, certainly the nurse did. Points off for both of them for choosing to just follow a chart and not thinking.

Why is the BMI Inaccurate?

The BMI is wrong not only in its two dimensional calculations but the inventor who was a poly mathematician and not a physician, Adolphe Quetalet never intended it to be used as it is today in the first place.  He developed the theory and invented a calculation in 1832 as a way to ‘define the normal man’ (humankind).  In 1972 Ancel Keyes renamed it the Body Mass Index and a much aligned and flawed ‘guideline’ was created.  In a sense it was a 182 year old hack.

However, the way it was taken out of context today and broadly implemented is scientifically, physiologically and logically wrong and it leaves out a very good indicator of overweight and obesity: the waist circumference.

“It’s one thing to estimate the average percent body fat for large groups with diverse builds, Keys argued, but quite another to slap a number and label on someone without regard for these factors.  Now Keys’ misgivings are gaining traction across the world of medicine: BMI simply doesn’t work when it comes to individual measurements.”

What works better:  Waist to Hip Ratio (WHR)

A much more accurate way of determining the kind of body fat is the WHR method.  This will point out the potential health risks depending on the ratio.  It is quick and as easy to record as the BMI yet is it not widely implemented.  One of the reasons is that a little more training and time is necessary and there is no official assessment chart.  That means that with WHR, the individual patient’s lifestyle history is an important factor as well (but shouldn’t that information be part of the initial visit anyway?).

In short, the BMI is the quick and easy method for doctors who can place assessment responsibility on a chart.  It is like putting blinders on a horse – no need to look left or right or think.  Just keep plodding the path, head those patients in, BMI them, push them a diet plan, head ’em out and call in the next one.

Keep in mind that any ‘index’ or ‘ratio’ is bound to be flawed because we are all individuals and there are too many variables to consider.  However, using the WHR for yourself and remembering it is a guideline is a very good idea.

That way, no one will look as foolish as that nurse did.


Tip:  Do an online search for more WH ratio information and calculators.  Most also have a metric version as well.

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