I wasn't really shocked by any of the photos in the slideshow. Each person appeared to fall into the definition of the BMI index. Clothing did get in the way but overall those defined as underweight looked it...as well as those in the obese and above.

What might be shocking to some is the subtle differences between "normal" and "obese". The word obese and the range of it in the BMI might be a bit misleading. Those on the "lighter" end of the obese range might not be seen as obese. Maybe a little better grading of the categories would be helpful.

The fact that I (a programmer who hasn't been to the gym in two years) and an average college linebacker have the same BMI shows just about how useful it is at measuring health... it entirely favors those who are thin, but have no muscle mass. BMI may be a vaguely useful scale for looking at a population as a whole, but it's pretty much worthless for measuring individuals, on its own.

showing average to thin sized women who's weight is less than mine doesn't do anything to blow my mind.  

I've been called average proportions but I think my number is bigger. 

I'm confused about how sharing my "number" will set me free.  I think it could tirgger my disordered eating again if I face the "reality" of that number and how far off it is from where it is "supposed" to be. 

Maybe this will work for some people, but weighing myself would put me right back into that diet mindset.

I don't understand how BMI is a social construction. It is a real, mathematical identifier. That doesn't make it a medically sound method of assessing health, or an entirely accurate scale along which to classify people visually and physically. It's medically outdated and has led to incorrect speculation and bizarre classification of many individuals, but I'm not sure that it makes BMI a "social construction" rather than just bad science.

There's also this: http://jezebel.com/5829156/new-website-allows-users-to-see-bodies-that-share-your-height-and-weight

I'm not sure what the point is here.  My impression is, BMI is not an attempt to attach social labels to people, but to help inform people as to whether they should try to lose some fat, in the interest of their health.  It's not a perfect measure.  If you can come up with a better measure, please do so and share it.  If one has resources to see a doctor and order tests, I presume one's diagnosis would be based on blood lipid and cholesterol and insulin levels and such.  But not everyone is in such a position.  Or, maybe better put, a high BMI is an indication that one should talk to one's doctor about whether one's fat levels are healthy or not.

Whether or not doctors understand the implications of excessive fat for health is another matter, which might be a matter of debate.  I don't know.

I see this as sort of analogous to the SAT as a measure of intelligence.  The corresponding chart would display people's career success or income or whatever, vs their SAT, and we'd see, occasionally, a person with "low" SAT does well and a person with "high" SAT does poorly.  OK.  The point of SAT is just to provide a quick measure of certain cognitive skills. People would be wise, if they have additional information, to use that information in addition to the SAT to present a clearer, more accurate picture of an applicant.  And they do.  Just like if you go to the doctor they'll collect more data than your BMI.  Both both tools are still useful as objective inputs into the analysis.  

I think it's important to be thoughtful about what is "good" and "bad" in all this.  It is bad to prejudice people, using one characteristic to presume another, unrelated one.  So it's bad to think that someone is "emotional" because one is a "woman" and it is bad to think one is "lazy" because one is "obese."  I don't think BMI is contributing to this; it's making no claims outside of health.

It is also bad when social signaling incentivizes unhealthy behavior.  So it is bad when smoking and doing drugs are seen as increasing attractiveness, and likewise if being overly skinny is seen as attractive.  I don't think BMI is contributing to this; "underweight" has the same negative connotation as "overweight," etc.

I sense that people want to conclude it is bad that weight matters at all, but I think this is naive.  An important biological imperative for any person is to find the best possible sexual partner.  We compete in many arenas on this front:  one wishes to be humorous, caring, intelligent, and physically attractive.  It's true that one's physical appearance is not totally in one's control; neither is one's intelligence or sense of humor and other qualities.  Indeed, it is perhaps more unfair for me to reject a woman because she is not very intelligent, than because she is overweight.  As social, sexual creatures, I imagine we are hard-wired to create hierarchies by which to compete for sexual partners.  Maintaining a certain physique is one of these.  If not for that, then intelligence / knowledge, or style, or wealth, or sense of humor, or whatever.  The point is people will always rank each other.  I'm not sure amount of fat is any worse than the others, so long it doesn't go into the situation mentioned above, where what is "attractive" coincides with what is unhealthy.

The "social construction" I see is the dangerous meme that it's "ok" to be fat, which this book about *health* from an *English* teacher further promotes..

As the population grows heavier there is a redefinition of "normal".  The average person is heavier, so what is "normal" now is to be heavier.  That's all well and good...until people do the very human thing and equate "normal" with "healthy", at which point it all comes tumbling down.

Carrying an unhealthy weight (often an extremely unhealthy weight) more and more is considered "normal" and in turn seen as "healthy".

Rather then face reality and address the actual problem (people are dangerously fat and visually less appealing), we try to BS ourselves and our neighbors into thinking that big is healthy and attractive.  We can fudge a little on the latter (attraction being heavily influenced by culture), but the fact that obesity is a huge health crisis can not be budged by simply thinking happy thoughts.

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While there are a few exceptions in the flicker gallery (mostly athletes), the overwhelming majority are very accurate.  If anything it's solid testimony of how highly accurate and reliable BMI really is for the "normal" population.

How timely...I avoid the scale and focus on measurement because I lift weights and I tend to gain muscle rather easily. I weighed myself yesterday and burst into tears.  Then I went and did 3 sets of 10 clean-and-presses with a 65 pound barbell.  I won't bore you with my squat weight. I lift because it makes me NOT want to choke the living sh*t out of people who think I'm fat, and more importantly, it makes me less likely to drive off a bridge in a fit of self-hatred.

...If you're serious about body fat ratios, which are a more precise measurement of 'health' than BMI, get a pair of calipers and measure that way. (Paging Ian Hacking and the history of statistics, I know.) 

I disagree with the idea that the BMI is a social construction. Having any kind of BMI score certainly has a lot of social baggage, but the BMI is a straight-up chart assigning numbers based on height and weight.

Of course, as a diagnostic tool, it's worse than worthless. It was invented by a statistician to track roughly how big his fellow countrymen were, not by a doctor at all.

It's not striking that so many of the overweight people don't look "fat."  What's striking is that most of the underweight and morbidly obese people look pretty healthy. 

I think the issue here is that BMI is using an objective measure of "how much mass a person has" and applying it to something that needs to be measured in a lot of different ways.  A person's weight affects their health, this is a fact.  But it isn't the number on the scale that defines that.  Is that weight muscle or fat?  If it's fat, where is the fat located?  Has this person always been over/underweight, or is this a relatively recent development?  If the weight gain or loss fast or slow?  And that's not even taking into account other related questions that aren't directly related to weight or "amount of fat or muscle" such as diet or excersise....

How are two women, both 5'8" but with a 25lb difference between them, (125/150), equally classified as "normal?"

BMI is a social construction.

No, it's not.  It's a formula that provides an approximation of one's body composition by using only two factors, height and weight. It is a guide, a benchmark to be used in conjunction with other benchmarks or reference points to health. It is notoriously inaccurate for athletes who are heavy because of muscle mass and certain groups.

Still, as a rough guide for people who are ignorant of the markers of health, I find it usually is pretty accurate; people who have high BMIs usually do need to lose weight.

I'm really surprised to such sloppy analysis on a site written by scholars.

Diabetes can kill you. Failing that, it can maim you.  It can cause vascular problems that destroy your cognitive function. 

It is not a disease to be lightly dismissed, and Type 2 Diabetes is strongly associated with being overweight.

I couldn't but notice that SI didn't feature pictures from the Flickr pool of two women who were about 5' 6" and over 200 pounds.  They fell into the "obese" and "morbidly obese" categories.  "Morbidly obese" is defined as 100 pounds over your recommended body weight. I have no trouble believing that a 250-pound 5'6" woman should weigh 150. 

Although BMI is not a perfect measure of health based on weight, nor was it intended to be, most of the people I know who have high BMIs are fat or obese by any measure.  They have been instructed by their doctors to lose weight because their weight endangers their health.  They may be pre-diabetic, or have hypertension, or have mechanical problems caused  by their weight.

Social Construct my ___.