Top Ten Reasons BMI Is Useless
10. Only Valid If You Happen to Be A 19th Century Belgian
The Body Max Index (BMI) formula widely used today was formulated 200 hundred years ago by Belgian mathematician Lambert Adolphe Jacques Quetelet. He was tasked by his government to devise a formula to describe the statistical distribution of obesity in the Belgian population at that time.
In other words, he took a bunch of data and came up with an equation to fit that specific data. It was, perhaps, useful for those people at that time to judge how they compare to their cohorts. That’s all. Quetelet himself recommended against using his equation on an individual basis to judge fitness.
If Quetlet had been a 19th century Samoan you can bet he would have come up with a different equation and most of us would be feeling pretty good about ourselves right now. And if he’d been a 19th century Masai, the line for the treadmill at your local gym would be miles long.
My point is, that the BMI calculation is only useful statistically and really tells you nothing about the health condition or level of obesity of a specific individual. People of different generations, ethnicity, ages, genders and lifestyles will have different ideal height to weight ratios.
It makes zero sense, and is in fact unhealthy, to tell a person of, for example, Japanese heritage that if their body does not match the statistical average of people in 19th century Belgium, they are unhealthy.
9. It Serves To Help Make Insurance Companies Richer
Go to any online BMI calculator. Do you know what you will see there? Ads for insurance companies.
Insurance companies love statistics and they especially love a statistical formula they can use as an excuse for placing reasonably healthy people into a higher risk category.
A healthy person with a high BMI is a dream-come-true for an insurance company CEO. They get to charge a high rate based on the widely used, and therefore legally justifiable, BMI for a person who is actually much less likely to ever use their insurance.
8. It Makes Doctors Lazy
Lazy is probably an unfair word. Doctors are in general some of the busiest people I know. And, exactly because of that, they are way too receptive of a diagnostic shortcut.
BMI index above 25? Get ye to the gym Margaret! Of course, there are other diagnostic tools the doctor could use but they would require more time and cost more money and the waiting room is already backed up.
7. Last Time I Checked, Women and Men Were Built Differently
The BMI formula was developed for the overall population of Belgium in the 19th century. Quetelet had no need statistically to make a distinction between the male and female population. The result is a formula that is not valid for either group.
It is true that some physicians use different BMI recommendations for men and women but the majority still use one set of widely published guidelines. A 2012 study in New York using more advanced methods of analyzing body fat levels concluded that the BMI number signaling obesity (today it is 30) should be lowered to 24 for women and to 28 for men. However, even that change is making the same statistics mistakes noted in point 10 above.
6. All Men (and Women) Are Not Created Physically Equal
This is a corollary to point 10. But goes a bit further. People come in all shapes and sizes. Even within a defined ethnic group you will find people of different body types. The healthy BMI ratio is determinant on bone structure, frame type, musculature and other variables. There is some truth to the old weight excuse, “He’s just big boned.”
The newest recommendations add waist and hip size (called the WHR) to the calculation but even this falls short of really accounting for body type differences.
5. It Causes People To Make Bad Decisions About Their Health
A recent study concluded that relying on BMI has led many women 50 and older to believe they are healthy when they are actually dangerously overweight. Conversely, they found that many men classified as obese may actually be their normal, healthy weight.
The researchers concluded that reliance on BMI as the measure of one’s need to lose or gain weight may be leading thousands of Americans to dangerous and erroneous conclusions.
4. The Obvious Cognitive Dissonance Causes People To Ignore Other Perfectly Valid Health Warnings
I gave a talk to my local rotary club when I was just in high school about cancer. (Thanks Rotarians!) I honestly don’t remember the point of the talk but I still remember the punch line. I gave a bunch of examples of ridiculous things that some research indicated may cause cancer. I remember hair dryers and burnt toast were on the list. Then I said, “Next thing you know scientists will announce saliva causes cancer…but only if consumed in small amounts over long periods of time!” It got big laughs (proof that Rotarians are kind people).
But I think I had a valid point. When we are presented with seemingly “scientific” conclusions that make no sense based on our real life experiences we tend to extend the disbelief to ALL such conclusions.
When we see obvious fit people whose BMI says they are obese or underweight we dismiss BMI advice and, because we’re often looking for an excuse to ignore bad news, we dismiss other healthy advice along with it, like stop smoking or eat your vegetables.
3. It's Scientific Bullying
Someone, decided, pretty arbitrarily (based on statistics no doubt) what is the perfect BMI range. Now, thousands of people are beating themselves up because they don’t fit someone’s conception of what their body shape ought to be.
Yes, obesity is bad for you. I’m not saying “live and let live.” If you are obese, please do something about it, now. But I am saying that everyone has a unique ideal weight and body shape that is determined by hundreds of factors. Cut yourself a break and let common sense and body awareness guide you to a weight that makes sense for you.
2. Because There Are Better Ways To Evaluate Your Weight
BMI is a shortcut. It is only useful in the extremes. If your BMI is over 30, yes you should see a doctor to evaluate if you should lose weight. You probably should.
If your BMI is below 18.5, your should see ask you doctor to evaluate if you need to gain some weight. You probably do.
But there are better ways for most of us to evaluate if we should lose weight. The gold standard right now is a technique called, DEXA (dual-energy X-ray absorptiometry). This is a body scan that can measure precisely your actual percentages of bone, muscle and body fat. DEXA is still expensive and, until someone invents a DEXA machine that is the size and cost of a bathroom scale, it will remain a test reserved for people who have already been diagnosed with a problem.
A second, less expensive, method is a blood test to measure leptin. Leptin is a hormone released by body fat. Leptin levels in your blood stream closely mirror the body fat percentages measured using DEXA.
For at home, there are now a plethora of on line tools for measuring either WHR or ABSI both of which take into account waist and hip circumference in their recommendations. These are still imperfect but a big step forward from basic BMI.
Finally, pay attention to the other signs your weight may be an issue. How are your blood sugar levels? How is your blood pressure? What is your degree of physical fitness? Do you lose your breath climbing stairs or just walking to the park? Listen to your body and your body will tell you when it has a problem.
1. Because This Guy Is Fat!
This is Lebron James. For those of you who don’t know, Mr. James is a professional basketball player (small forward - Cleveland Cavaliers). He is widely considered one of the best players currently in the game. (Lebron haters, please just substitute the player of your choice. This ain’t ESPN.)
Looks to me like he’s in pretty good shape. But his BMI is 27.4.
Quick, Lebron, Call your doctor! You are dangerously overweight.
Seriously? I picked on Lebron James because he’s no stranger to controversy and probably won’t mind one more. But, I could have used literally hundreds of professional athletes as examples. (For you ladies, does the name Serena Williams ring a bell?)
If you need evidence that the BMI method of evaluating weight is in need of serious revision look no further than your TV. Some of the most physically fit people on the planet are overweight, underweight or even obese according to their BMIs.