Body mass index (BMI) was intended to categorize research participants on the basis of their height and weight, and not as a way to determine health, argues Brandy W. Root, RDN.
She says, “BMI was developed by a Belgian mathematician who wanted to determine the metrics of the average man to better understand human physicality and social aptitudes. No peer-reviewed research exists stipulating that a BMI of 24.99 makes a person healthy, while a BMI of 25 makes them unhealthy. But, in our attempt to quantify all aspects of the human condition for insurance reimbursement, we have allowed BMI to become a determining factor in care.”
The obvious concern with BMI is that it only accounts for sheer mass and not the type of mass. Excess body fat is linked to increased risk for cardiovascular disease, while excess muscle mass is not, but we do not routinely assess body composition; but simply look at a patient’s weight and give them a stamp of ‘normal’, ‘overweight’, or ‘obese’. So, for example, those working in construction or other physically demanding jobs may be exceptionally well muscled and capable of impressive physical feats, but are marked as ’obese’ because of their BMI.
Bioelectrical impedance analysis – which involves allowing a weak current to pass through the body from the hands to the feet and determines body composition on the basis of the speed at which the current travels through different tissues – may be one alternative. It may not be appropriate for all patients, specifically those with pacemakers, but it is generally an accessible and accurate method to retrieve quantitative measurements of fat mass to track a patient’s body composition instead of just viewing all weight the same way.
However, Root argues that medical professionals should not get rid of BMI from assessments if they want patients to continue to receive the best care, but that they should also focus on other indicators of wellness alongside BMI, such as weight loss trends, blood pressure and frequency of bowel movements. “Why am I not referring to a patient’s BMI? Because it’s as relevant to their health as their preferred flavour of protein shake. That’s to say that it doesn’t matter to me. I am worried about my patients’ health and wellness, and BMI is at the bottom of my list of concerns.”
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