August 23, 2017

Why I don’t calculate BMI for my clients

Just the other day, a client attending his first health consultation asked me, “so now can we find out my BMI?”  He was surprised to find out that I was not interested in his BMI despite his goal to shed a few pounds.

In fact, body mass index (a.k.a. BMI) is a limited tool for assessing health risk.

Here are four reasons why I don’t use BMI in my health assessments:

1. BMI refers to a number that is a result of dividing a person’s weight by his height.   This number is supposed to reflect whether or not you have a healthy body weight for your height. It assumes that a high BMI means an individual is over-fat and that a person with a low BMI is unhealthy. Often, this is not the case, and people prematurely slot themselves into categories associated with the appropriate level of risk for cardiovascular disease, diabetes and cancer.  Maybe you have genetic or lifestyle factors that increase your risk of these disease, but maybe you don’t. BMI does not consider this information.

2. BMI does not take into account frame size. Large frames consist of denser, heavier bones, while smaller frames are lighter. If you come from a large -framed genetic stock you will probably be heavier than another person who shares your height. This fact means that the large-framed individual so with a healthy body composition with ample muscle, they are considered “obese” by BMI standards.

3. BMI can’t tell you how much of your weight is muscle.  An NHL player may weigh 200 pounds, but he has to be one fit specimen to have the endurance to play a fast game like hockey.  Take his weight and his height, and just based on that he is considered obese.  This is simply untrue.

4. BMI charts assume that tall, slim people are underweight.  I’d know, because I am one of those people.  As far as I’m concerned, the pantyhose manufacturers still haven’t got it right, because they assume that being tall means being heavy.  Consequently, it’s tough to find the right pair! Having said that, I’ve met many women with hourglass figures who turn out to be dangerously over-fat. Why? Because muscle doesn’t make women look like this—fat does.

So, what did I offer the client who wanted to know his BMI?  A BIA—bio-impedance analysis of his body composition. As a nutritionist I find this to be a far more useful and accurate tool to assess health risk and monitor whether or not weight loss or gain is healthy or unhealthy.

Have you had your body composition measured, and if so, were you surprised by the results?

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