Have you been told by your doctor that your BMI is too high?
Or maybe the criticism is coming from your health insurance, or that health tracker you just started to use.
Even though you know you could stand to lose a little weight—who doesn’t?—it doesn’t feel great to see it in black and white.
You’re overweight, and you need to do something about it.
My Wake-Up Call
This summer, I took my daughter in for her annual checkup a week after she got back from a holiday with her grandparents.
Her grandparents had jars of sweets scattered around the house. My daughter freely helped herself. I wasn’t surprised to see that she’d put on weight. But I wasn’t worried.
Once my daughter was back in her normal routine, I knew her weight would get back to normal.
At the doctor’s office, my daughter stepped on the scales and got her height measured. The doctor showed us her growth charts. She was in the 97th percentile for both height and weight.
Then the doctor said:
“Her BMI is high. We would recommend trying to bring that down.”
And launched into a discussion on healthy eating and exercise.
Until that day, I’d never talked to my daughter about weight. We talked about being strong and nourishing our bodies with healthy food, but we never talked about being fat or skinny.
But on the way home from the doctor’s office, I felt I had to. “We’re going to have to be more careful about the sweeties from now on, honey,” I said. “The doctor wants you to lose a little weight.”
Little did I know that my words were unleashing Pandora’s box.
My strong, beautiful daughter—who’d never thought twice about her weight before—was hearing me say she was fat.
The Truth about BMI
If only I’d known then what I know now, I would have done things differently.
A few weeks later, a fellow mother told me that she’d got the same advice for her children—despite the fact that her son was skinny as a rail.
“They say that to everyone,” she told me. “Don’t worry about it.”
But I did.
So I did what I always do: I went online and researched.
I discovered that nearly half of individuals classified as “overweight” or “obese” from their BMI are actually completely healthy.
Even more surprisingly, nearly a third of individuals classified as having a “normal weight” are actually unhealthy…
Once their blood pressure, cholesterol, insulin resistance, and other metabolic tests are taken into account.
The study concluded that about 75 million Americans are misdiagnosed on the basis of BMI.
Why are we using BMI at all, then?
The History of the BMI Index
Today, we expect our doctors to use the most precise measuring tools available.
We’re not living in the 1800s. We expect digital precision.
Yet the formula behind BMI—body weight divided by height squared—was developed by a Flemish astronomer and statistician back in the 1800s, as a way to describe the “average man.”
It would have been consigned to the dustbins of time if it weren’t for American physiologist Ancel Keys.
By the 1960s, the recognized authority for determining ideal weight was Metropolitan Life Insurance. They developed a set of charts that set an individual’s ideal weight based on gender, height, and age.
In 1972, Ancel Keys challenged the validity of those charts. He argued that a better gauge of weight was that old formula, body weight divided by height squared. He even coined a new term for it: body mass index.
A decade later, the World Health Organization (WHO) followed suit. They embraced BMI, eventually dividing the numbers into four categories: underweight, normal, overweight, and obese.
Until 1998, the National Institutes of Health considered anyone with a BMI of 27 or less normal. But once they decided to adopt WHO’s guidelines, millions of Americans who’d previously been normal were now considered overweight.
Because the average BMI among Americans ranges from 24 to 27, this new classification meant that half the American population would always be overweight or obese.
Does it really make any sense to consider 1 in 2 Americans unhealthy?
Only if you’re a weight loss company…
Or an insurance company.
The Bigger Problem with BMI
If BMI were just a convenient way to estimate one’s ideal weight, that would be the end of the story.
The real scandal is the way BMI has been used by the medical industry and insurance companies to penalize folks who score on the high end of the scales.
Imagine going to a checkup and finding out that your BMI is 31.6. Your doctor tells you that you’re obese and need to take immediate steps to lose weight. But your name is Valerie Adams, and you’re a two-time gold medal Olympic athlete. Are you going to listen?
The medical industry has long known that BMI is not an accurate measure of body fat. The more athletic or the taller you are, the more likely your BMI will land you in overweight territory.
And if you’re on the short side, your BMI will paint you as slimmer than you really are.
NPR “Math Guy” Keith Devlin calls it “mathematical snake oil,” going on to say:
It is embarrassing for one of the most scientifically, technologically and medicinally advanced nations in the world to base advice on how to prevent one of the leading causes of poor health and premature death (obesity) on a 200-year-old numerical hack developed by a mathematician who was not even an expert in what little was known about the human body back then.”
Alternatives to BMI
If you really want to know whether your weight is in a healthy range, forget BMI.
As Yvette Brazier writes for Medical News Today, “A healthy weight is hard to figure exactly. One size does not fit all.”
Your ideal weight depends not just on your height but also on your gender, age, body type, bone density, and muscle-fat ratio.
Although there are alternatives to BMI, it might be best to look past weight entirely and focus on other indices of health, like metabolic markers and body fat percentage.
But the medical industry is still deeply invested in BMI. It’s a quick and easy way to categorize people. It’s much less expensive than more accurate alternatives.
I wish with all my heart that I’d never said anything to my daughter about her weight.
Not long after that doctor’s visit, she asked me for the first time in her life, “Do you think I’m fat, Mummy?”
When she started school in September, she came home after the first week and said that one of her new friends thought she’d lost weight.
I was horrified. For years, I’d deliberately kept the words “fat” and “skinny” out of our home. Now, thanks to her doctor, my daughter was self-conscious about her weight…
And she would never get that innocence back again.
It’s up to us—as parents, as patients, and as women—to stop letting weight define our health.
Weight and health are not synonymous.
And it’s time the health industry got the message.