This Is Why BMI’s Wrong About Ideal Body Weight

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Hello Lovelies:

If I told you to take your weight in kilograms and divide it by your height squared, you’d probably look at me a little funny, right?

What if I said that the answer to that equation decided whether or not you’re healthy? Sounds bonkers, right?!

But that’s exactly what the Body Mass Index (BMI) does. The formula for BMI is weight in kilograms divided by height squared. And the results apparently decide whether of not you’re at an ideal body weight or unhealthy.

But that’s a vast oversimplification of a very complex subject. Health isn’t decided by something so simple. And it was never meant to be.

So let’s talk about it! Today we’re going to dive into why BMI doesn’t necessarily decide your health outcomes…

Weight Fluctuations And Graves Disease

It’s me <3

As many of you know, I have Graves Disease. And one of the symptoms I experience during a flare up is weight loss. It happens quickly and it’s typically pretty noticeable.

Guess what happens when a flare up causes me to lose weight… I get so many complements! People look at my smaller body and assume this must mean that I’m healthy and doing great. My smaller size merits more respect due to our unfortunate societal norms.

But even though I become smaller and have a lower BMI, I’m unwell in this state and need medical help.

BMI and societal beauty standards on weight would assume that I’m healthier in my autoimmune hyperthyroid state.

1. BMI was Never Meant to Measure an Individual’s Health

The Body Mass Index was never meant to decide whether you’re healthy. It was actually created with the idea of community health in mind. Kind of like how Q-Tips were never meant to be used inside your ear – we’ve all been using BMI in an unintended way this whole time.

The mathematician who invented the body mass index, Adolphe Quetelet, created his formula almost 200 years ago to help the government decide how to allocate health funds to the general public. (source)

Instead of deciding if someone was at an ideal body weight, BMI was supposed to quickly measure the approximate health of a large population.

Even Ancel Keys, the scientist who popularized the use of BMI in the 1970s, stressed that BMI should be used to determine the health of a population, not individual people. (source)

Clearly no one took Ancel’s advice…

Related: This Weight Watchers App Is The Worst (It’s For Kids?!)

The ultimate problem is that BMI oversimplifies an incredibly complex thing. You can’t decide if someone’s well just by looking at their weight and dividing it by their height squared. You can’t even look at someone and know everything about their well-being.

Which brings me to…

2. BMI Doesn’t Accurately Predict Health Outcomes

Body Mass Index is so widely used to determine your health… but according to studies BMI actually shouldn’t be used as a way to measure body fat or to decide if you’re healthy. (source)

Why? Because health outcomes do not necessarily match up with your BMI.

While we’ve been taught to believe that falling into the obese category automatically means that you’re not healthy, that’s not exactly true. In this study, people who had a BMI of over 30 (obese) either experienced more health issues… or were healthier on average than those who, according to BMI, were at an “ideal body weight.”

It went either way. Showing that BMI outcomes are not accurate in determining your health.

But wait, there’s more!

This study found that those in the overweight category had lower mortality rates than those the Body Mass Index favoured as “normal.”

Does that mean that you should worry if you’re naturally in the “normal” category. No. The point is that your body will settle where it functions optimally at. We’ll talk more about that soon. But, essentially, everyone’s optimal weight is different. If you’re healthy and well, that’s what matters. And BMI can’t decide that for you.

We need to stop automatically assuming that where someone falls on the BMI scale determines their health, be it “normal” or not. And, since our collective knowledge of BMI and body size has informed our opinion on the health of those around us, we should also stop making assumptions about someone else’s health at a glance.

Fun fact, a new Canadian guideline states that obesity should not be defined by weight alone. Instead, it recommends that obesity is defined by someone’s health instead of just their weight. Needed change is coming baby!

Related: Working On Awesome Lifestyle Changes? Avoid These 5 Mistakes

3. BMI Guidelines Changed Overnight

In 1998 the National Institute of health changed their BMI guidelines. Suddenly you were considered overweight if you had a BMI of 25 instead of 27.8. (source)

Overnight 29 million Americans went from normal weight to overweight.

Of course, this change in the BMI scale served to increase overweight and obesity numbers. And thus the “obesity epidemic” was now a bigger problem.

While the decision was in part to try to meet then standards of the World Health Organization, apparently they also felt 25 was an easier number to remember. (source)

I don’t know about you, but that seems like a silly reason to classify someone’s weight as unhealthy to me.

And problematic changes continue to this day.

In 2013 the American Medical Association (AMA) passed a resolution that recognized obesity as a disease. Even though their own Committee on Science and Public Health advised against it (in a five page paper no less). (source)

The Committee stated that obesity has no actual symptoms and isn’t always harmful, which goes against the definition of a disease. And, as we already know, it can be protective for some and even sometimes lead to better health outcomes. (source 1, source 2)

The Committee also worried that labeling obesity as a disease may ultimately hurt people by adding to already prominent and problematic stigma. And by also increasing medical bias and leading to unnecessary treatments.

But the AMA decided to move forward with their resolution anyway. Further feeding into the unfortunate societal idea that BMI and obesity can accurately predict health outcomes. (source)

4. You Can’t Look At Someone And Know Their Health

Fun fact, sumo wrestlers typically have low rates of heart disease and diabetes and tend to be quite healthy. They also happen to have larger bodies and a high BMI. (source)

BMI doesn’t take into account:

• Muscle Mass
• Bone Density
• Race
• Gender
• Fat Distribution
• Type of Body Fat (Subcutaneous Fat and Visceral Fat are very different)

This is a major reason why health outcomes do not typically match up with someone’s BMI. It’s an unreliable source that only looks at a tiny part of a very large picture.

When it comes to our bodies, one size definitely doesn’t fit all.

So there really isn’t any such thing as an overall ideal body weight based on height.

We’re are all naturally different. We also all fluctuate in different ways and for different reasons. And that’s ok! You are still worthy of the same love and respect always, no matter your size. And you can still be healthy if your body isn’t naturally whatever BMI tells you it should be.

Related: Why The Quarantine Fatphobia Needs To Stop

5. Weight Bias Affects Quality of Medical Care

Fatphobia and weight bias are problematic and prevalent forms of societal discrimination that reliance on BMI perpetuates. (source)

And it also affects medical care. (source)

Patients with a higher BMI are more likely to:

• Receive less empathy from doctors
• Be stereotyped by doctors as weak willed and/or lazy
• Encounter more disrespectful comments from health care providers
• Experience bias medical treatment

This ultimately leads to poor quality of care and has a massive affect on someone’s well-being. 

Empathy from your doctor, for example, not only leads to better care, it also makes you more likely to follow their medical advice. Because you trust that they have your best interest at heart. Which ultimately helps you get better!

But those who don’t receive that empathetic care and, instead, experience fatphobia in their doctor’s office are less likely to follow their doctor’s advice. And they might not seek out preventative care in the future, for fear of experiencing the same hurtful treatment. (source)

Bias treatment also means that weight is sometimes blamed as the cause of unrelated health issues. Leaving the real culprit unexamined and untreated. And unfortunately that only leads to unnecessary and preventable suffering and pain. (source)

This is a whole lot of not ok.

6. “Normal” BMI Doesn’t Always Equal Healthy

You can absolutely have a “normal” BMI and be healthy. But having a BMI that’s considered “abnormal” doesn’t necessarily mean you’re unhealthy.

We’ve already talked about a study that found that those in the overweight category often fared better than those BMI favoured as “normal.” And that those considered obese were sometimes healthier on average than those who had a “healthy weight” according to BMI.

And yet we still assume we can decide someone’s health at a glance based on their size. Or that we know what an “ideal body weight” would even look like.

Final Thoughts

Health is a very complex thing affected by many factors. More than a simple mathematical equation could ever take into account.

We’re all very different. All of your bodies are different from mine. Your genetics and environment are completely different from mine. The exercise you enjoy, the food that makes you feel awesome, the stress relief activities that work for you… you guessed it; all different!

What matters is that you feel well and are doing well. And if you’re not well, that you have access to the medical care you need to get better. Oh, and self-acceptance and self-love go an awful long way too <3.

There are a lot of things that work together to determine your well-being. But BMI and it’s obsession with determining your ideal body weight and theoretical health outcomes is not one of them. I propose we leave it behind with other outdated practices from the 1800s, like leeching and doctor’s not washing their hands (seriously).

What are your thoughts on BMI? Any outdated health practices or current wellness ideals you’d like to say goodbye to? Share your thoughts and experiences with me in the comments below.

Health and love,

Thought of the day: Some things are best left behind.

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