63. BMI is BS (+ Why Health is Way More Complex)

BMI has been used for decades as a quick way to measure “health” — but here’s the truth: it was never designed for individuals. Created in the 1800s by a mathematician and adopted by insurance companies in the 1970s, BMI ignores body composition, genetics, fitness, nutrition, and mental health. Yet it’s still used to label and shame people in ways that often do more harm than good.

In this episode of Sturdy Girl, I break down the history of BMI, why it’s a flawed measure of health, and what to focus on instead. I share my own story of walking out of a doctor’s office when BMI was used against me, plus research that highlights better, sturdier ways to define health. Most importantly, you’ll learn practical steps for doing a “sturdy health check-in” that has nothing to do with a chart.

In this episode, you’ll learn:

• Where BMI really came from (and why it was never meant for you)
• The major flaws of BMI as a health measure
• Why focusing on weight alone misses the bigger picture of health
• Research-backed alternatives like Health at Every Size (HAES)
• A simple “sturdy health check-in” to measure progress beyond numbers

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Stay Sturdy, friends.

Transcript

Jess: Hello friends, and welcome back to another episode of Sturdy Girl. This is episode 63. we are in season six. Today we're diving into a topic that has probably touched every single one of us at some point. That is BMI Body Mass Index. You know that number that your doctor might rattle off that supposedly sums up your entire health in one label, underweight, normal, overweight, obese.

Here's the thing, and you probably likely already know this. BMI is bullshit. Not because our bodies don't matter. But because this number doesn't measure what we've been told it measures. It doesn't measure health, it doesn't measure our worth. It doesn't really tell us a whole hell of a lot, and yet it's still used as if it does. So in this episode, I'm gonna give you the backstory of where BMI even came from, why it fails, and most importantly, what actually matters more for your health and your sturdiness.

I am not going to be, how do I say this? This isn't a total BMI takedown and I won't pretend to be the expert on BMI. This is just on a Google deep dive rabbit hole to learn about the roots of BMI, knowing and explaining why it's bs, right? And then also for us to just actually talk about things that matter when it comes to our health.

So. Backstory. Let's rewind for a second, because BMI, it wasn't even created by a doctor and it wasn't even designed for individual health.

It was actually first developed in the 1830s by a Belgian mathematician named Adolf Ketelet. He was studying the average man by looking at population level data. I probably butchered his pronunciation. He's Belgian, but it was in an area of Belgium that speaks French. And Blake is probably cringing as he is listening to this and wanting to correct how he said his name, but whatever.

He studied the average man, population level data. This formula weight divided by height squared. This BMI was never intended as a measure of personal health. It was a population statistic. Plain and simple.

Fast forward more than a century. And along comes Ansel Keyes, an American physiologist you might recognize from his work on diet and heart disease. In the 1970s. Keyes compared different ways of estimating body fatness across large groups, and he found that Ketelet's index, what we now call BMI, lined up well enough to be used as a general tool.

Here's the important part. Even Keyes himself said BMI was best suited for population level research, not as a diagnostic tool for individuals, still, because it was easy, cheap, and quick, insurance companies and healthcare systems adopted it. And before long BMI was being used to label individuals in ways it was never meant to.

Okay, here's our origin story. This is our villain origin story. Let's talk about why this fails when we take something that's meant to be population based and make it individual.

One, it does not measure body composition. A muscular athlete and a sedentary person with the same height and weight can have the exact same BMI. Even though their health profiles are very, very different. Two, it ignores other factors. Genetics, fitness, nutrition. Mental health, sleep, stress, none of that is captured.

Three, it's biased. BMI was developed on European white dudes, so it does not translate well across genders, ethnicities, or diverse body types. And four, it doesn't predict health outcomes the way that we think. In fact, there was a massive meta-analysis in JAMA in like 2013 that looked at nearly 3 million people and found that those in the so-called overweight BMI category actually had lower all cause mortality than those in the quote normal category, which just shows BMI. Categories do not line up neatly with actual health or longevity.

And to make this personal, this isn't just abstract for me, like I've been on the receiving end of BMI weaponization, if you will. Um, probably a decade ago or so, I had a primary care provider and I was in the middle of marathon training and I was working on a, like pretty significant volume block.

Averaging, I wanna say somewhere between 40, 45 miles a week, maybe closer to 50. And I was eating a lot, strength training. All the things, right? So very, very active and not really thinking about my body size.

At that point in time, it was more like, am I eating enough to sustain this level of activity, right? So I go into this new primary care. The medical assistant sees you first, right? They take all your vitals down, all the things, and. Technically with my height and weight at the time I was put into either it was like the upper end of like overweight or into that like obese category.

Either way, not the quote unquote normal category. This doctor walks in and she sits down at the computer. She has not my eye contact. She says hello. She introduces herself and goes directly to my BMI and says. Okay, so we need to talk about your body mass index and, and your weight. Um, can you tell me a little bit about what you are doing to take care of your body?

What, what is your exercise routine? Because we need to talk about you losing some weight. And I paused and I was like, oh my God. Ma'am, can you look at me for just a second please? I am running marathons. I'm training for a marathon. I have run multiple already in my life. I'm eating well over 3000 calories a day to keep up with my activity levels.

Can you look at me for just a second, make eye contact and talk to me about this. And it was just like. The most ridiculous experience of my life. In fact, I'm pretty sure deep in the archives, there is a blog post somewhere that I wrote, but I actually walked outta that appointment because there was no advocating for my body or my habits or my lifestyle or anything to this person because all they wanted to see was that BMI.

And yeah, so that moment it really stuck with me and it's one reason why I'm so passionate about helping my clients redefine health outside of a single number, a single metric. Okay, so that was a total side tangent. I just, I couldn't not include that because it was such a profound experience, especially where I am also a healthcare provider.

Um, and that piece of active listening and compassion is so, so important. Anyways, here is the truth about health, and you know this already. Health is way more complex and way more sturdy than BMI gives it credit for. Health is multifaceted. It's not one number. And here are some, some sturdier measures of health.

One strength. Can your body carry your groceries? Lift a suitcase, keep you steady and going on a hike. Interestingly, there's actually research to support that. Your grip strength, so talking about like lifting suitcases, carrying groceries, carrying your kids around. Grip strength is related to your longevity.

How's that for nerdy science? Number two, cardiovascular fitness. How is your heart and lung endurance? Do you get winded going up the stairs or can you walk, run, or bike comfortably? Jokingly, I'm gonna say, please don't talk to me about this right now because I currently have a tiny ninja growing in my belly and encroaching on all my organs, including my lungs.

So we currently winded going up the stairs, but I know that it's temporary. And number three, daily behaviors. Are you fueling your body with food moving regularly? Sleeping enough? Managing your stress. Another thing indicative of health is our mental health. Do you have tools for coping? Do you have a supportive relationship with yourself, with your partner, with a friend, with family?

Those things are so freaking important, and it's more than just one number. And then five, quality of life. Can you do the things you love and do you feel connected to your body in those moments? I serve a very significant elderly population within my dental hygiene work. This is one of those pieces, this quality of life and talking about all these other health metrics that I am learning is so, so, so much more important.

And in fact, now that I'm saying this, there's actually a book, I wanna say it's called The Good Life, and it's based on the Harvard study that has been going on for 80 some odd years now, but essentially boils down. The measure of a successful life as the quality of our relationships. So do with that what you will when we talk about health, but there you are.

Then while we're talking research, um, there is a review from a nutrition journal on the health at every size movement, and it found that when people focused on behaviors like balanced nutrition, enjoyable movement, and self care, they saw improvements in things like blood pressure, cholesterol, eating behaviors, mental health without focusing on weight loss, on metrics on a number alone.

I suppose like shameless plug here, just real quick, like this is where my coaching comes into with my clients. It's not necessarily chasing numbers. Sure, we might work towards a running PR or a triathlon PR or something, but we look at how are you feeling? How are you performing, what kind of habits are we building, and the sturdiness that you're creating for the long haul.

Like these are the things that are important. So let's make this practical as we're talking about BMI being Bs If BMI has been weaponized against you, here are three sturdy takeaways.

The first one, remember what it is? BMI is a population tool. It was never meant to define your personal health. Number two. You have options at the doctor's office. You can absolutely request to skip being weighed or you can also ask not to discuss BMI. You absolutely have the right to say, I do not find BMI to be a helpful measure for my health.

Us talking about it, knowing it's BS is not going to change the fact that insurance companies and healthcare systems use this metric. It is what it is. If you wanna go and dismantle that, that's a whole nother thing, but knowing it's still gonna happen within the office, advocate for yourself so that you don't have to take part in that conversation if you don't want to.

And then third, third takeaway, do a sturdy health check-in. Ask yourself, am I moving my body regularly? In ways I enjoy? Am I fueling with enough food to support energy and recovery? Am I getting decent sleep? Am I practicing self-compassion when things don't go perfectly? Those things are sturdier than BMI will ever be.

So bottom line, BMI is Bs because it reduces a whole ass human to a single number. You are more complex, more resilient, and more sturdy than a chart can ever measure. Okay, friends, sturdy humans. If this episode resonated with you, follow the podcast, subscribe so you don't miss what's next. And if you know someone who's ever felt defeated by their BMI or the BS surrounding that, share this with them.

It might be the reframe that they need.

And hey, if you wanna work on defining health and strength on your own terms, that is exactly what I do with clients. You'll find details in the show notes. If you're looking for a strength training program for endurance athletes. The Doors to Grit our Signature Strength Training Program are still open as of the release state of this podcast and will be open.

Gosh, through the 15th of September, I had to think about a calendar. Okay, next week we're talking about pregnancy and postpartum body image. There's actually been some really rad research out in the last year or so, and I'm ridiculously excited to share it with you in a fun and sturdy way. So be sure to tune in next Friday when the episode drops.

Until then, stay sturdy, my friends, and I'll talk to you soon.