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How useful is the body mass index (BMI)?
www.health.harvard.edu ^ | Posted March 30, 2016, 9:30 am , Updated June 22, 2020, 12:00 am | Robert H. Shmerling, MD

Posted on 09/17/2020 8:59:38 AM PDT by Red Badger

Robert H. Shmerling, MD Senior Faculty Editor, Harvard Health Publishing

Do you know your BMI? Increasingly, people know theirs, just as they know their cholesterol.

If you don’t know your BMI, you can use a BMI calculator available online, including this one at Harvard Health Publishing. All you need is your height and weight. Or, you can calculate it yourself, using this formula:

BMI = (Weight in Pounds x 703) / (Height in inches x Height in inches).

So, now that you know your BMI, is it worth knowing? What are you going to do with it?

What your BMI means

To understand what your BMI means, it’s useful to take a step back and understand what it’s measuring and why it’s measured.

BMI is a calculation of your size that takes into account your height and weight. A number of years ago, I remember using charts that asked you to find your height along the left side and then slide your finger to the right to see your “ideal weight” from choices listed under small, medium, or large “frame” sizes.

These charts came from “actuarial” statistics, calculations that life insurance companies use to determine your likelihood of reaching an advanced age based on data from thousands of people. These charts were cumbersome to use, and it was never clear how one was to decide a person’s “frame size.”

BMI does something similar — it expresses the relationship between your height and weight as a single number that is not dependent on “frame size.” Although the origin of the BMI is over 200 years old, it is fairly new as a measure of health.

What’s a normal BMI?

A normal BMI is between18.5 and 25; a person with a BMI between 25 and 30 is considered overweight; and a person with a BMI over 30 is considered obese. A person is considered underweight if the BMI is less than 18.5.

As with most measures of health, BMI is not a perfect test. For example, results can be thrown off by pregnancy or high muscle mass, and it may not be a good measure of health for children or the elderly.

So then, why does BMI matter?

In general, the higher your BMI, the higher the risk of developing a range of conditions linked with excess weight, including:

diabetes

arthritis

liver disease

several types of cancer (such as those of the breast, colon, and prostate)

high blood pressure (hypertension)

high cholesterol

sleep apnea.

According to the WHO, nearly 3 million people dye yearly worldwide due to being overweight or obese. In addition, independent of any particular disease, people with high BMIs often report feeling better, both physically and psychologically, once they lose excess weight.

And here’s why BMI may not matter

It’s important to recognize that BMI itself is not measuring “health” or a physiological state (such as resting blood pressure) that indicates the presence (or absence) of disease. It is simply a measure of your size. Plenty of people have a high or low BMI and are healthy and, conversely, plenty of folks with a normal BMI are unhealthy. In fact, a person with a normal BMI who smokes and has a strong family history of cardiovascular disease may have a higher risk of early cardiovascular death than someone who has a high BMI but is a physically fit non-smoker.

And then there is the “obesity paradox.” Some studies have found that despite the fact that the risk of certain diseases increases with rising BMI, people actually tend to live longer, on average, if their BMI is a bit on the higher side.

Should we stop giving so much “weight” to BMI?

Maybe. There are studies suggesting that BMI alone frequently “misclassifies” metabolic health. For example, found that:

More than half of those considered overweight by BMI had a healthy “cardiometabolic profile,” including a normal blood pressure, cholesterol, and blood sugar.

About a quarter of people with normal BMI measures had an unhealthy cardiometabolic profile.

Actually, this should come as no surprise. BMI, as a single measure, would not be expected to identify cardiovascular health or illness; the same is true for cholesterol, blood sugar, or blood pressure as a single measure. And while cardiovascular health is important, it’s not the only measure of health! For example, this study did not consider conditions that might also be relevant to an individual with an elevated BMI, such as liver disease or arthritis. In addition, more recent studies (such as this one and this one) suggest that those who are healthy and overweight or obese are more likely to develop diabetes or other negative health consequences over time.

Bottom line

As a single measure, BMI is clearly not a perfect measure of health. But it’s still a useful starting point for important conditions that become more likely when a person is overweight or obese. In my view, it’s a good idea to know your BMI. But it’s also important to recognize its limitations.


TOPICS: Business/Economy; Food; Gardening; Health/Medicine
KEYWORDS: bmi; bmicult; bmiindex; bodymassindex
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To: KarlInOhio
BMI is indexed to a world-wide average. You are being compared to a Somali as well as a German.

If half of Americans are "overweight" then basic statistic al evaluations dictate that you must re-evaluate your sample base to get rid of bias.

Americans should be compared to their peers i.e. North Americans or first world samples because 98% of the world is overweight compared to Somalis.

41 posted on 09/17/2020 10:22:37 AM PDT by pfflier
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To: Red Badger

I think maybe you’re on to something red


42 posted on 09/17/2020 10:24:35 AM PDT by Karliner (Heb 4:12 Rom 8:28 Rev 3, "...This is the end of the beginning." Churchill)
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To: TexasGator
V = Pi * r^2 * h

Volume of a cylinder? What does that have to do with BMI?

43 posted on 09/17/2020 10:26:39 AM PDT by pfflier
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To: pfflier
Ideally it shouldn't be "average" - it should be "healthy". If everyone is a fat ass that doesn't make it healthy. Now, how do you match height to weight without considering body type or body fat percentage? Can't do it.

On the other hand, my doctor could do the scene from Airplane where Johnny says "And Leon's getting larger" for my diagnosis rather than the BMI.


44 posted on 09/17/2020 10:31:23 AM PDT by KarlInOhio (In 2016 Obama ended America's 220 year tradition of peaceful transfer of power after an election.)
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To: Red Badger

I suspect once tbe progressive democratic communist party of America takes over the government again it will be used to deny medical services to anyone with a higher bmi than the charts indicate it sould be.


45 posted on 09/17/2020 10:33:52 AM PDT by Ronald77
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To: Dr. Sivana

Depends upon the location of said “dyed hair”.


46 posted on 09/17/2020 10:35:04 AM PDT by NativeSon
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To: Ronald77

I think it already is......................

https://www.freewayinsurance.com/knowledge-center/health-insurance/understanding-health-insurance/health-insurance-for-obese-people/


47 posted on 09/17/2020 10:35:45 AM PDT by Red Badger (Sine Q-Anon.....................very............)
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To: Red Badger

What does it mean when my BMI is higher than my IQ?


48 posted on 09/17/2020 10:36:20 AM PDT by Yo-Yo ( is the /sarc tag really necessary?)
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To: PIF

LOL


49 posted on 09/17/2020 10:36:36 AM PDT by Salamander (The left screams out in pain as they stab you.)
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To: Yo-Yo

It means that you are a ‘fathead’..................


50 posted on 09/17/2020 10:37:30 AM PDT by Red Badger (Sine Q-Anon.....................very............)
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To: Red Badger

I went to a BMI calculator. I am 5’11”. I entered my height and actual weight of 175 pounds. The calculator says my weight is normal. I entered 195 pounds the calculator said that is normal. I entered 145 pounds the calculator said that is normal. When I entered 200 pounds I finally got an abnormal (over weight) reading. The results are all over the place,


51 posted on 09/17/2020 10:38:21 AM PDT by forgotten man
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To: Red Badger

I would have to lose about 40 pounds to not be “obese.”

My doctor doesn’t concur with that based on my structure. He thinks I should lose about 35.

He has me confused. So, I just stopped trying.

(I am kidding. I could lose 45 pounds.)


52 posted on 09/17/2020 10:49:51 AM PDT by Vermont Lt
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To: cdcdawg

Right, the BMI is a simple metric for tracking body composition trends in populations over time. When used in that way—as a statistical tool—it works just fine. When it’s applied to individuals it just causes confusion.


53 posted on 09/17/2020 10:51:40 AM PDT by Yardstick
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To: saleman

saleman wrote: “I don’t know why she couldn’t have just quit eating so much and excercised some but it worked for her....!”

I suspect you do not need to lose 100 pounds. It’s well known that exercise and diet do not always result in significant weight loss. Your body will fight losing weight. As you diet, your metabolism will decrease making exercise difficult. About the only way diet and exercise will result in significant weight loss is if you’re on a draconian program like in a POW camp.

I’ve had weight loss surgery and it’s been wonderful. I’m down 80 pounds, blood pressure is down forty points (no longer taking 2 bp pills a day), resting heart rate is under 50.


54 posted on 09/17/2020 10:53:28 AM PDT by DugwayDuke (A Man Hears What He Wants to Hear and Disregards the Rest)
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To: cdcdawg

As a lot of medical measures are these days, its a back of the envelope screener. If you are a big person, muscular and wide...they can do caliper tests or even still do the immersion/displacement test.

But, for the most part the key readings are done in total, and a profile is done.

My doc goes though my weight, blood pressure, blood enzymes, blood glucose, and cholesterol and comes up with some sort of index.

My weight and blood pressure haven’t changed much in 40 years—and my blood pressure was always low—so low it hindered me from jobs like flying because they were afraid I would pass out.

It was a curse as a youth—but now at 60 I feel blessed.


55 posted on 09/17/2020 10:54:58 AM PDT by Vermont Lt
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To: Yardstick

Well stated. It’s a telescope, not a magnifying glass, so to speak.


56 posted on 09/17/2020 11:00:56 AM PDT by cdcdawg (Biden has dementia.)
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To: Karliner

LOL


57 posted on 09/17/2020 11:08:23 AM PDT by angcat (THANK YOU LORD FOR PRESIDENT TRUMP!!!!!)
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To: KarlInOhio

and even the thin people are often classed as overweight


58 posted on 09/17/2020 11:30:00 AM PDT by Secret Agent Man (Gone Galt; Not Averse to Going Bronson.)
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To: Red Badger

Test: Stand naked in front of a full length mirror.

You will get your answer on whether you are fat/obese or not.


59 posted on 09/17/2020 11:37:48 AM PDT by dakine
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To: Dr. Sivana
...nearly 3 million people dye yearly worldwide...

I think the last time I dyed anything I was 4 or 5 years old and it involved Easter eggs.

60 posted on 09/17/2020 11:37:51 AM PDT by Verginius Rufus
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