BMI stands for Body Mass index, most of us have heard of it, may even fear it! But, do you really understand what doctors use this for?
The body mass index was developed by Adolphe Quetelet. He was a Belgium astronomer, mathematician, and sociologist who enjoyed accumulating and studying statistics from 1830-1850.
His equation was originally called the Quetelet Index. It was not until 1972 that the term BMI was introduced. Quetelet developed the formula as an attempt to quantify the amount of tissue -bone, fat and muscle in a human-taking into account their height and gender to determine their fitness.
The formula is rather straight forward and it is easy to calculate your BMI.
But there are many debates as to how accurate or useful this number, by itself, is for categorizing an individual as normal, overweight or obese.
After calculating your BMI, your health care professional uses that number to determine your category, which should help determine your likelihood of developing a number of disorders such as Type II diabetes, cardiovascular disease or certain types of cancers.
But, how accurate is this really?
I found this out first hand, when our daughter the nationally ranked gymnast, went for her annual checkup. She was 8 years old and just beginning to compete. She was a burly 2nd grader, to be sure, as most kids in her class did not have washboard abs and cut triceps.
She was short, barely making it above the x axis on the growth chart. The pediatrician looked at her weight and calculated her BMI, something that was pushed for by the state, as they were collecting data on childhood obesity rates. The doctor laughed as she turned toward us and said, “Alexandra, you are overweight!”
I understood the joke but Alex did not, and was confused since she had some friends who were truly overweight, and she did not believe that was her situation. We had our first “this is what healthy looks like” talk.
The reality is that, when Quetelet developed this equation, there were factors that he was not able to control. It was impossible for his formula to take into account that muscle is heavier than fat. Dense bones are heavier than light ones.
The fact that athletes, who tend to have more muscle and less fat, and the elderly, who tend to have less muscle mass in general, demonstrates that the BMI equation can not accurately categorize their health.
Great examples of those for whom the BMI system does not apply are gymasts, who tend to be muscular and short, and basketball players, who tend to be muscular and taller than average, these extreme body types throw the equation off.
Additionally, bigger muscles need denser, stronger bones in order to form the correct attachment points. The elderly generally have bone density loss and smaller muscles.
Unfortunately, there are those individuals who use this discrepancy to disregard this information, when they should not!
While it can be misleading, BMI can be a real diagnostic tool for those people who are not muscular or elderly! There will always be people who prefer to lie to themselves then face the facts!
So we have a system that the government, and insurance industry, use as their standard of relative health that discriminates against athletes and the elderly population.
Another level of confusion is introduced when arbitrary categories are assigned to the BMI values. For example the World Health Organization (WHO),working in conjunction with the Centers of Disease Control (CDC) lowered the overweight cutoff from a BMI of 27, to 25. This decision moved millions of Americans from the overweight to obese classification. What a nice surprise to wake up to that day!
And that leads to a lot of confusion and misunderstanding as we all try to sort out what information is helpful, and what is not.
So what should we be using?
Waist circumference is a potentially useful tool to determine how much visceral, or abdominal fat one is carrying. Studies have linked high levels of abdominal fat to a variety of life shortening ailments.
Regardless of your height or BMI, you should try to lose weight if your waist is:
- 94cm (37ins) or more for men
- 80cm (31.5ins) or more for women
Even so, there is debate about how best to measure your waist circumference, as many people take this measurement differently.
Still harder to define is the waist to hip measurement, also used, in order to determine a healthy ratio. When researches observed people taking these two measurements the subjects rarely placed the tape measure in the correct “waist’ or “hip” areas, skewing the numbers.
So, if you are really wondering about your overall health, what can you do?
Get your percent body fat measured! This is the best measurement to take to determine if you are at risk for problems down the road. Generally speaking, less than 20-25% total body fat is the goal, and ladies we have a higher percentage of fat than the men. It ok!
There are a number of ways to calculate body fat percentages, and I have included two great references for more information for you to consider.
Bottom line: No one number or calculation can accurately asses your overall health. But that is not an excuse to ignore it either! Be honest with yourself and stop stressing over numbers. Get moving and eat good food, and see your doctor regularly. 😊
Body Fat Percentage information