Is BMI really BS?

Sorry I have to totally disagree with Iwishyouwell, BMI as a number for an individual is totally, completely and utterly useless.

It is an extremely antiquated formula (originally known as the Quetelet Index) and simply doesn't give an accurate representation of health unless you happen to be a sedentary person of average height. It's main flaw is based on the way it is calculated, which is mass / height^2. The common argument is that if you have a good lean body mass, and muscle is more dense than fat, your BMI will be high when you perfectly healthy, but the main problem is that is starts from a datum of a standard height, and then scales up or down depending on if you are shorter or taller, but tall people aren't just scaled up short people, the formula breaks down as soon as you start to move away from the datum and the further you move away the more inaccurate it gets. Many, many studies have show it is useless for indicating cardiovascular disease, heart attack, stroke, and it's not even a great indicator of diabetes.

In short, ignore BMI. If you want a simple measure of health, the waist to height ratio has proven much more effective, but really you need to measure body fat percentage, either with a pair of callipers or with a set of scales that can detect resistance. The scales tend not to be too accurate in there reading of BF%, but anything is better than BMI.

Also checkout the Body Scale Index, which has been developed to overcome the shortcomings of BMI.

http://absi-calc.appspot.com/

So 2 months ago I was considered "overweight"...sorry I have to laugh...at 160lbs..in a size 5/6...not overweight...

Clothing sizes is about the worse marker available when determining appropriate weight.

Almost all clothes in the US are vanity sized, and women's clothing has absolutely no regulations or standards. A 5/6 today can be so vanity sized that it was a 10-12, or higher, in decades past. Even men's clothes no longer follow the actual inches printed on the waist sizes. Hell I have two pairs of jeans from the 90s in a size 36 that are smaller than some size 33s today.

The mirror and your health markers are the best standard, clothing size the absolute worse.

BMI doesn't distinguish between fat and muscle so it's certainly massively flawed

Pick any muscly athlete and BMI will say they are overweight

eg. Running back Adrian Peterson

And yet how much of the general population has a body built like a professional running back?

I'm 210# @ 6'2" with a BMI of 27 (Overweight): my current BF is 20%, so I'll buy the BMI determination. However, I'm currently progressing towards my goal to recomp to 210# @ 15% BF, which would put me squarely in the 'athletic' range. My BMI will still be 27 and will not reflect any of the positive change I will have made. So how is this a good metric?

It's a good metric for the general population.

The general population is not "6'2" looking to "recomp" their body to 210lbs at 15% bodyfat".

All general metrics have outliers. Every single one. Slating a general system to compensate for a minority outlier is senseless.

Obviously if someone has a higher than usual lean mass, yet are lean and rocking a low body fat level, they're not a candidate for the BMI range. But how much of any given population fits into this criteria?

And why is it that most countries in the world have populations that fit well within the BMI range, yet it's almost always Americans who are railing against how wrong the BMI is?

The BMI is a poor metric to apply to individuals (esp. individuals that are not 19th century Belgians ) because it ignores the square/cubed law in order to keep the math simple.

Here's a link to an interesting read about the science behind the flaws: http://people.maths.ox.ac.uk/trefethen/bmi.html

And a link to an alternate calculation that accounts for the fact that people are three dimensional and provides a comparison of the two measures: http://people.maths.ox.ac.uk/trefethen/bmi_calc.html

Bottom line: BMI is a poor analog to measuring BF% (and thus level of 'health') - in consistently underestimates BF% for shorter people and overestimates BF% for taller people. If you're taller than average, you should think twice before taking drastic measures to hit an arbitrary BMI number.

My $0.02

Yet, once again, BMI isn't a static number. It has built in a very wide range. Most people are going to be able to find a healthy, fit weight within a BMI ranging as radically as 30 or so pounds.

Most. Not all. But most.

So 2 months ago I was considered "overweight"...sorry I have to laugh...at 160lbs..in a size 5/6...not overweight...

Clothing sizes is about the worse marker available when determining appropriate weight.

Almost all clothes in the US are vanity sized, and women's clothing has absolutely no regulations or standards. A 5/6 today can be so vanity sized that it was a 10-12, or higher, in decades past. Even men's clothes no longer follow the actual inches printed on the waist sizes. Hell I have two pairs of jeans from the 90s in a size 36 that are smaller than some size 33s today.

The mirror and your health markers are the best standard, clothing size the absolute worse.

BMI doesn't distinguish between fat and muscle so it's certainly massively flawed

Pick any muscly athlete and BMI will say they are overweight

eg. Running back Adrian Peterson

And yet how much of the general population has a body built like a professional running back?

I am not from the states...and I can tell from the mirror that I was not overweight...and to your point of vanity sizes...I am 41...put my prom dress on while I weighed 165lbs...yes a 20 year old dress...so no vanity sizing there...I was 135lbs when I graduated...it fit like a glove....it was a size 8....I was not overweight at 165 either even tho BMI put me there...

Here is some more history on BMI...it was developed to help the government ie monarchy, distribute goods during lean times in Europe...

Even health care professionals are saying BMI is not the gold standard as it once was thought to be...

As to the professional athletes being in the overweight or even obese category..no they aren't typically but let's be realistic.

Lifters outside of professional athletes and people with larger frames are going to not be able to rely on BMI...me being one..

I have a large frame, I lift heavy and at 165 I was in a 20 year old size 8....I was not obese. I am a normal everyday woman, just like lots of woman here...BMI for individuals is rubbish period....it is good for "general population" in groups.

If you somehow manage to fit in BMI ranges as an individual that means you are "like the average" but that doesn't mean we all are.

congratulations on making your weight goal!

Q: are you stil going to use MFP?

So when did all these massive BMI outliers evolve?

In 1960 US average for men was around 166 lbs.
Today the average is about 196 lbs.

Yet height has only increased in an average of about 1 inch.

It's interesting to note that all this backlash against BMI and the old height/weight charts started when we got much, much fatter. Now people are screaming about the muscular outliers, and so many people are suddenly spinning tales of how they're perfectly skinny/small/lean at much higher weights than the average person ever was before.

Did we evolve over the last 50 years? Did we collectively become these massive, muscular running backs? Why did so many men and women fall within the healthy BMI range just a few decades ago, but now it's suddenly super skewed and totally wrong to use BMI?

Eh? This isn't a backlash against BMI, this is just the usual evolution of knowledge

there are a large number of people in the general population that either aren't too bright, or don't really care - hence why food manufacturers had to go from supplying nutritional information on their packaging, to providing a 'traffic light' system of Red = Unhealthy, Green = healthy - to cater for the ignorant!

So BMI is useful for those that just need a simple indicator. For those such as the OP, and dare I say it, the majority of MFP users on the forums who have chosen to take an active interest in their weight/health, BMI is far too simplistic

What next? If BMI is deemed too complex for the populous to understand, how about...
"Grab hold of stomach and wobble up and down - if it jiggles too much then you are overweight" That would work for the majority would it not?

So when did all these massive BMI outliers evolve?

In 1960 US average for men was around 166 lbs.
Today the average is about 196 lbs.

Yet height has only increased in an average of about 1 inch.

It's interesting to note that all this backlash against BMI and the old height/weight charts started when we got much, much fatter. Now people are screaming about the muscular outliers, and so many people are suddenly spinning tales of how they're perfectly skinny/small/lean at much higher weights than the average person ever was before.

Did we evolve over the last 50 years? Did we collectively become these massive, muscular running backs? Why did so many men and women fall within the healthy BMI range just a few decades ago, but now it's suddenly super skewed and totally wrong to use BMI?

This isn't about anything but how and what BMI was developed for...it was developed for groups of people not indiviuals...it was taken as gospel and used for individuals later...doesn't make it right...

We aren't just talking about the US either...if we are talking world wide...average height and weight will vary depending on race.

For example in Guatamala average height of a man is 5 ft 2...a woman is 4 ft 6...vs Dinaric Alps 6 ft1 for a man and 5 ft 7 for a woman...

In Canada average height for a man is 5 ft 8.5 and a woman is 5 ft 3...I am 5 ft 7...I am not the average Canadian woman...and neither are half my friends they are all taller so why should we apply averages to ourselves...my son is 6 ft 3..husband is 5 ft 11, brothers are all over 6 ft tall..why should we apply "average" calculations...

BMI is antiquated and being used for something it wasn't meant for...we have increased out knowledge and therefore should look for better measurments of health...

And to your point of the 60's we also thought leaded gas was fine then too but with increased knowledge and science we now know it isn't...just because it worked back then doesn't mean it will work now.

BMI is one metric, and that is it. I personally don't use it at all as I think it is a VERY generic and inaccurate way to view health. Listen to you doctor and your own body.

I think the only people on the planet to whom you should listen regarding your weight loss goals are your doctor, and the person in your mirror, but that's just me.

Most doctors are not up on weight loss and nutrition. A dietitian would be much better.

that said for 90% of the population BMI should give you a pretty good indication of your weight. If you tend to have very little muscle, or a lot of lean mass then the scale would be off, but that isn't the majority of people. but is only meant for comparing populations vs. populations, not any one person vs. the scale, that is misuse of BMI, not something inherently wrong with BMI

i was told BMI isn't really accurate for me as i'm very short for my age, making me an outlier. with my BMI i'm on the border of healthy/overweight, but i've calculated it using different sites and they're all different with the range of my 'healthy' weight.
I think it's always best to take it into consideration as a rough guide but not to rely to heavily on it. My doctors always say my weight is fine so, yeah.