Riley Houston RD
- July 27, 2022
- 12:13 pm
The term BMI (Body Mass Index) is known universally, and it’s been hailed as a valuable tool to estimate your body fat. People learn to use this number because they have been told over and over again by doctors, fitness instructors and the media that it is an accurate assessment of body composition. However, the reality is things are entirely different.
Although BMI is used globally in most medical institutes for assessing and diagnosing body composition, it is rooted in corruption and unvalidated literature. Moreover, it shows no semblance to actual body composition. So then why is it still being used?
A Brief Intro To Body Composition
The body is made up entirely of nutrients; carbohydrates allow cells to function, fats create structure and communication, and proteins do the rest. So our bodies are just compartments of varying sizes for nutrients. Body composition is then looking at these nutrient compartments and determining where they are, quantifying them, and comparing them to get a ratio.
Body composition is instrumental in determining metabolic function, defining deficiencies and malnutrition, and monitoring health outcomes. All body components must be looked at individually and as a whole. For example, I can’t say your fat mass is too high without looking at your protein stores. Nor can I tell you you’re dehydrated without looking at your electrolytes.
There are a few conflicting theories as to what the components of the body are. For example, some say we comprise fat and fat-free mass; others argue we are more complex with fat mass, muscle mass, lean muscle mass, water, and bones. But the premise behind them is to look at multiple components and compare them to each other, which is where BMI is flawed.
Get expert advice on the purpose of your body components and what is right for your body.
The Origins of BMI
The vast majority of us have had our BMI calculated by a doctor, personal trainer, or your scale at home. Though incorrectly, most health professionals use BMI to assess and diagnose body composition and nutrition status. However, few can elucidate the origin and history of this favourable equation, and if they could, they likely would tell you BMI is nonsense.
BMI is simply the use of a statistical equation called the Quetelet equation developed by Belgium Mathematician Lambert Adolphe Jacques Quetelet in the 19th century. It’s a simple equation relating weight (in kilograms) to height in meters squared. He created the equation to measure body mass composition, despite his lack of health, physiology and chemistry education.
Although developed in the 1830s, Quetelet’s equation only gained popularity after the 1940s. There was a strong desire to determine ‘healthy body weight and an index to compare it to. It was a noble goal because a healthy weight has endless benefits for a person’s well-being and quality of life; it makes sense that finding and quantifying a healthy weight could improve the lives of so many. But then why was BMI researched so thoroughly? It doesn’t even consider age or sex but can still tell if you’re obese.
Just like with all scientific research, funding is needed, and you need investors that see a benefit in the study; so who funded BMI studies? Insurance companies noticed their clients were getting heavier, requiring more medical care, which is costly for insurance companies. So to spend less and earn more, they needed their clients to get healthier or raise their prices.
That’s where the true beauty of weight comes in; it’s controllable. Weight is, to an extent, manageable; with enough incentive, motivation and correct diet, most people can lose weight, and if they don’t, they can be penalised with a fee increase. The same can’t be applied to cancers or infections (such as Tuberculosis) since those are somewhat ‘uncontrollable’. All that was left was to define a weight range, justify it with literature and make it known to the public. That’s precisely what the companies did. Studies were done for years on limited populations and demographics until BMI was recognised by NIH, WHO, and health organisations worldwide.
Why Do We Still Use BMI?
A massive amount of literature on body composition is centred around BMI. But, read any of the studies, and you will find flaws such as limited populations, lack of RCT and peer reviews, so why do most health professionals continue to use it?
The simple answer is that it’s easy. It’s incredibly convenient to plug a patient’s weight and height into Quetelet’s equation and determine if they are malnourished (meaning underweight and overweight). A doctor seeing over 100 patients daily can calculate all their BMI on their phone while doing rounds.
It also costs nothing to use BMI to assess body composition – taking skinfold measurements and calculating body fat % is time-consuming, attaching electrodes to measure bioelectrical impedance is complicated and slow, and using an MRI can be extremely costly.
Finally, BMI is simple. It doesn’t take much to understand a BMI value or educate someone on it. It doesn’t take much to understand a BMI value or enlighten someone. All the health professionals must show the BMI value and tell the patient if it’s too high or low and then lose or gain weight respectively. A health institution that is understaffed, overworked, and underpaid will take BMI as a diagnostic criterion over any other known method. That’s why it’s still used and is still being taught at most health science and medical schools.
Finding a health professional that goes further than the simplicity of BMI is important – gain a new perspective on your body, and book your consult today.
How to Interpret BMI Values
Considering what I said above, it’s easy to understand why BMI is still being used – and why Health professionals will continually use it until the following easy, simple, and cheap method. So why not learn to interpret the values yourself so you can make your judgement on your own body?
As we know, BMI is expressed as kg/m2, whereby reference ranges are given. A healthy weight (BMI) is considered anything between 18.5 kg/m2 and 24.9 kg/m2; if you are within that range, congratulations, you probably have a healthy weight! Anything below 18.5 kg/m2 is considered underweight. For children, there are more specific ranges and classifications.
Overweight and obese are grouped according to the WHO into three classes.
- Obese Class 1: 30 – 34.9 kg/m2
- Obese Class 2: 35 – 39.9 kg/m2
- Obese Class 3: ≥40 kg/m2
Originally these were the only values needed to diagnose obesity. Fortunately, updated guidelines (EOSS staging tool) use BMI and health status to stage obesity from 0-5. This means you can be classified obese class 3, but because you show no signs and have no health implications, you are diagnosed with obese stage 0.
Although BMI is logically flawed and physiologically wrong, it doesn’t mean being overweight or obese is too. Obesity is a pandemic plaguing the world and disease that ruins millions’ lives. Justifying obesity should become taboo just as it is to promote detrimental health behaviours (like substance abuse and poor hygiene). Body composition analysis is valid, logical, and beneficial.
If you are worried about your weight, don’t rely on BMI; instead, get another test done; there are so many cheap and affordable scales available that measure BIA and more and more practitioners are moving away from BMI to perform more detailed analyses in addition, most public gyms today have scales to measure BIA and body composition.
Want to find out more about your body composition? Book your consultation with me for a unique diet experience.
