What is the Body Mass Index?

Allow me to make a gentle, uncontroversial statement: the Body Mass Index is the most self-destructive diet aid since tapeworms.

About a century ago, hucksters sold chewing gum that promised to help people lose weight without dieting. The gum worked but at a terrible cost: it contained tape worm eggs. The eggs hatched into worms inside a person's intestinal tract, the worms sank their fangs into the small intestine, and then they ate food as it came along. People lost weight because they were slowly starving. The Body Mass Index isn't that horrid but it is that unscientific. It is completely unsupported by medical research.

Adolphe Quetelet, a Belgian mathematician, created the BMI formula in 1832. In 1832, when leeches were used to cure people. In 1832, when surgeons didn't know that they had to wash their hands before surgery. Quetelet designed the BMI as a way to describe large populations and he said repeatedly that his formula did not apply to individuals, but this didn't stop it from being used — or misused — in just that way. Almost 200 years later, doctors misuse the BMI for patients, trainers misuse it for clients, and worse, it is misused by those annoying weight charts that you see in many doctor's offices. Weight charts are all based on the BMI and they all give bad advice.

The Body Mass Index and weight charts have no place in modern medicine. If your doctor uses them and if you are anything but a small person who is not very muscular, run screaming from his office and find someone who does not use medical techniques from 1832.

The Insurance Industry Strikes Again

The Body Mass Index assumes that everyone who is the same height should be at the same weight. Men, women, old, young, everyone in the world! If their height is the same, their weight should be the same. This is perfectly reasonable when used to find the average weight of a very large group of people, but it is ridiculous when applied to individuals. As a result, broad people, muscular people, tall people, almost everyone who is not small framed and shorter than average is branded as being overweight by the BMI.

And this offered a golden opportunity to the life insurance industry.

The industry got serious about using the BMI in the 1950's. Actuarial trolls were dispatched to create a weight chart — a BMI-based chart that could be used to make normal people look overweight when they applied for life insurance. That meant they could be charged higher premiums. The trolls had no interest in helping overweight people; instead, they build a weight chart with ludicrously small allowances for sex and frame size and with no other considerations at all. As a result, more than half of the people who applied for life insurance were tossed into the ‘obese’ category and their rates went up.

That corrupt weight chart, over sixty years old and never updated, is still found in doctor's offices all around the country. It is a disgrace.

How do you know if your doctor is using a weight chart based on the BMI? Simple. It is the only weight chart ever produced anywhere. Ever.

How the Body Mass Index is computed

The BMI predicts your ‘ideal’ weight based on just one thing: your height. (Formula below.) It says that everyone who is the same height should be the same weight. This is nonsense. Here is a real example:

I am a 5′ 10″ man with a very broad, muscular frame. My mother is a slender, sedentary 5′ 10″ woman. According to the Body Mass Index, we should both weigh the same amount! It says that if we want a healthy BMI of 22, we should each weigh 153 lbs. And so should everyone else in the world who is 5′ 10″. In the real world, at 153 she would be overweight and I would be dangerously underweight.

In general, if a man and a woman are the same height and have the same percentage of body fat, he will weigh significantly more than she does. Men tend to have bigger muscles and denser bones. This extra weight means he will have a higher BMI than she does. He may be told that he is overweight while she is told that she is normal. In reality the exact opposite might be true.

The BMI system couldn't be worse if it was invented by Congress. We all need better advice. That is why I invented The Weight Zone.

The Weight Zone

I'm a mathematician; I designed The Weight Zone to be much more accurate, much more useful than the BMI. The Weight Zone is powered by an algorithm that considers 25 different factors: body statistics, health history, and lifestyle. It tells me that my Ideal Weight Zone is between 194 and 210. If I weigh more than 210, my chances for heart disease, stroke, and diabetes will go up. If I weigh much less than 194, I might become underweight. I'd operate below my peak and be less able to fight off wasting diseases such as cancer. Of course, if I reached my BMI — suggested weight of 153 I would be hospitalized.

My mother, on the other hand, is very different. She is 84, diabetic, has heart disease, and watches too much TV. She only weighs 146 pounds, 7 pounds less than the BMI says she should, but that is still too much. Her Zone is between 129 and 139. This makes sense. She will be healthier and feel better if she takes off just a few pounds. On the other hand, the BMI says Mom should weigh 153. Mom is 84. If she gained seven more pounds, she might need to go on insulin.

Perhaps the best part of the Weight Zone is this: it changes as we change. If my mother begins a modest exercise program and improves her eating, her Zone will change. She won't need to lose as much weight to control her diabetes and heart disease. I already exercise regularly. More exercise won't change my Zone, but if I stop I'll need to lose 19 more pounds! How do I know? I used the Weight Zone Calculator. It's a great tool.

Doesn't this make sense? If you want to know how much you should weigh, shouldn't the answer be based on your health history and your lifestyle, not just on your height? Don't you want a reasonable, achievable goal instead of an impossible to reach 'perfect weight'?

The BMI Formula

For those of you who still remember your high school math, here are the formulas — unchanged since Adolphe Quetelet created them in 1832:

BMI = (Weight X 703) / Height²

Weight = (BMI X Height²) / 703

If you think that these formulas are not relevant to your body, you're not alone. I'm a professional mathematician and I think the formulas should have stayed in 1832.

If you have questions or comments, please write to me. My email address is below. Jay Wiener,Founder and CEO jay@weightzonefactor.com