Rant: BMI measures

I'm not a fan of the BMI scale. I just don't think that it is very accurate - and this is supported by facts and research. Now, before I go on, let me put a WARNING. The BMI (body mass index) scale is sometimes needed. For example, we use this all the time to help patients lose weight, to gain weight, and to monitor growth in children and teens. But what I am not fond of is the preoccupation with BMI, when really, we might be losing the bigger picture of things.

First, what is BMI? You can calculate yours by dividing your weight in kg by the square of your height in m. Generally, 18.5-24.9 is normal, less than 18.5 is underweight, and more than 25 is overweight. But what is wrong with this, you might ask? Well, all this measures is your height and weight. It does not take into account other factors, such as muscle mass. If someone with a lot of muscle used BMI, they would likely be in the overweight section. But are they overweight? No. They simply have more muscle, which makes their weight higher. But it is muscle, not fat; thus, they are not overweight. Let's consider another example. What about a child who genetically has bigger or thicker bones than others (yes, this is possible). Their bones will be heavier, but are they fat? No. Their bones just weigh more. But a clinican might not know this, and thus assume that the child is overweight. If we all used BMI in this way, we might mistakenly think that we are overweight and need to lose weight - when really, the measurement is not taking everything into account.

What about when helping ED patients? Many treatment facilities use BMI, as this is their only reliable predictor. Generally, patients are considered 'weight restored' if their BMI is 20+. I'm not arguing with this - I understand that BMI is needed as some way of deciding when patients have gained enough weight. But, really, everyone is different. Maybe I am healthy at a BMI of 22, and not 20. So why should my treatment team decide that I no longer need help for my eating disorder? What if I need to gain more weight than a BMI of 20 in order to be healthy? Or what if someone without ED has beena t a BMI of 18.5 their entire life. Are they sick? Probably not. This may be due to genetics, their way of eating/living, and other factors. Maybe this person does not need to gain more weight, unless other factors necessitate it. Should we force this person to eat more simply to gain more weight? If they are healthy and eating enough, probably not. Do you see why BMI is a 'gray' measurement to use? It is hard to determine when it is useful, and when it is not accurate.

However, I know that BMI provides us with some useful information, and that is why we still use it today. I'm not saying that this is wrong. I am simply giving a warning out there to people who use BMI. For some, this might create an obsession and possibly lead to ED. For others, their BMI may be in the overweight area when really, they are not overweight. For others, their weight may be lower and underweight on the BMI scale, even if they are healthy. For all patients with ED, however, recovering is more than just the BMI scale! I was weight restored quickly, but my thoughts and eating patterns did not improve for a while. So, please do not get stuck with the idea that as soon as your BMI is in the 'healthy' range, you are cured from ED. It is more than just the number. YOU are more than just a number. So, be cautious. Medicine/science/math can come up with theories and equations to help us, but that does not mean that all of these subjects/ideas are flawless.

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