Is the BMI useful?

Perhaps most Americans at some point have seen the Body Mass Index, which tells you your ideal weight. Unless your name is Lindsay, chances are you are “overweight” to “obese” by their standards and better stop cutting back on the beer and frankfurters. I’m all for public health initiatives, and tend to buy into the fact that as a country we’re too fat and gotta cut back on the beer and frankfurters. But the BMI seems to have body image issues on behalf of a nation. My ideal weight is 153 lbs! That’s at the high end of normal. They consider the low end of normal to be something like 119 lbs! They are obviously operating under some different definition of “normal” than mine, since it seems to me that 153 lbs. would be rather thin and 119 would make me look like an extra in Schindler’s List. I’ve seen several people react the same way to these figures (pun intended). So here’s my debate… first, are the BMI figures correct? Are we just operating under a fat-friendly lens, thinking of fat as normal and normal as skinny, or are they really off? Second, and more importantly, is it self-defeating to encourage America to try and achieve these weights? I’m on weight watcher’s myself, and have already lost ten pounds. When I realize that I still need to lose nearly 30 more pounds just to be on the fat side of normal for these guys, I think, “forget that! pass the pizza!” I think this is exactly what happens with lots of people. Instead of educating the bulging masses about proper diet, they just discourage people and/or make people dismiss the whole BMI thing as silly. If they want us to back off of the beer and frankfurters, wouldn’t it be more productive to give people realistic ranges of weights? Or, again, is that just a distorted, American, used-to-being-fat-and-seeing-fat perspective?

I have no cite for this, but my understanding is that the BMI is really an insurance industry tool. Not especially accurate, but it’s quick. Getting valid information of this kind involves individual testing and evaluation.

Real body mass indicators will take into account your build (fine boned, big boned, etc). The simple weight/height ones are mostly just for basic starting information…

Ideal weight is more than just a function of body mass index. Calculation of ideal weight should also take into account famililal body habitus, the individual body habitus, menstrual “threshold” weight, weight history over developmental milestones, frame, age, and activity levels.

It’s simply one tool among many. Generally speaking, adolescents can be expected to be at the low end of the BMI chart or just below, and BMI tends to increase as the decades pass.

I thought the thread title referred to the music-licensing authority, the alternative to ASCAP.

The history and logic behind the current terms can be found in this excellent article.

In short, the current terms are from the WHO and are used because they were simple, easy to remember, consistent with then world-wide distributions of weight, and captured the essence that morbidity increases with BMIs over 25. They are also very limited in utility. The overweight though have never been the target of intervention; the obese have.

The update is that in American today those with BMI’s of 25 to 29.9 do have increased morbidities (increased rates of diabetes, high blood pressure, dyslipidemias, etc.) but paradoxically have the lowest mortality rates. That only seems to go up, and goes up dramatically, as one gets to BMI’s over 30.

One third of Americans have BMI 25 to 29.9 and they have the lowest mortality rates. Me, I’d call them normal.

For a full debate on the merits of focusing on fat please see this recent thread. Upshot: probably better to focus on lifestyle than on fat per se, to focus on dietary habits and activity levels than the scale, not only because those matter at least as much as the fat but because that is how you most effectively change body habitus long term. Stigmatizing the obese is counterproductive. Most important prevent obesity in the first place. Figure out what we eed to do in our society to prevent the lifestyles developing in the young that are associated with obesity and its huge long term costs to our society. Real many dollars and cents costs, not only health costs.

It’s a shame that you can’t search on BMI, because this has been discussed many times before. And in every discussion, someone will come along and give the right answer–that it’s very accurate for large groups but not so hot for individuals, and that it’s frequently misunderstood and misapplied–but their posts always get glossed over in favor of folks pointing out that they personally are healthy despite their BMI, thank you very much.

I dunno, I don’t think 153 is as thin as you think. I’m 5’8" and weight somewhere between 155 and 160 and I’m right at the upper limit of my BMI “normal” range. I don’t think I’m really particularly thin. I have a very nice layer of pudge on my belly and a decent amount of muscle mass.

I’ll echo ultrafilter here, though. It’s a stastical tool based on what’s accurate for a large population sample. It may not be accurate for individual body types.

Just to echo Ultrafilter on the off chance that two posts catch better than just one…

BMI is very useful looking at POPULATIONS but not very useful for INDIVIDUALS.

What does that mean, for you? It means that for you, BMI may have no particular usefullness or significance. If other indexs (inexi?)or circumstances indicate that you’re weight is healthy, then BMI may not be for you.

To use a personal example, I have a BIG family Hx of Type II diabetes that seems to hit women in my family once they hit 35, even if they’re only marginally overweight (ie BMI 26-27). It’s probably in my best interests to keep my BMI at around 22 or 23 which is what it is at around 140-145 lbs (I’m 5’8"). So given my particular family history and body type, BMI is a very useful tool, but that’s a fluke, as opposed to an indication that BMI works for individuals.

I’ll disagree just a bit. It is one useful bit of data for an individual just not enough on its own. A BMI over 30 is a major red flag. Odds are great that that person has significant excess fat and has some room to improve on lifestyle choices. Screening that person regularly for diabetes is indicated. And for high blood pressure too.

Unless of course that person is short, or elderly, or an athlete.

It seems like a reasonable measurement in my case, but obviously something as simple as weight divided by height is not going to take into account other important variables.

I’m currently hovering right around 25 (5’11", 177 lbs), which is the border between normal and overweight. I do feel that my ideal weight is about 10-15 pounds less than I currently am, which puts me firmly in the normal range. However, the bottom end of the normal range is way low. I could weigh as little as 133 pounds and still be “normal” weight. The lightest I’ve ever been at this height was about 150, and that’s when I was running X-Country in high school and ran 40 miles a week on average. I was skinny. Like, “count all the ribs” skinny… I can’t imagine being 133 pounds and not being considered way underweight.

Ultra, no, over 30 is still usually a red flag for health problems for the short, elderly, and even for the athletic. Maybe a football lineman or a weightlifter might get there without being over fat, but not most athletes.

The elderly have less muscle mass, so a BMI of 30 is even more worrisome. The scale is adjusted for height, so shortness has nothing to do with it. It is true that athletes are off, but I can’t help but wonder if far more people are saying the BMI isn’t right for them just because they don’t like what it says.

The point is, though, that the model wasn’t developed using these populations, and as such, it’s not sound to extrapolate to them.

Forgive me for being literal, but if you say “A unless B” then it strikes me that you are saying “if B, then not A.” A BMI of over 30 IS, indeed, a red flag for the elderly (it’s an even redder flag), and I’ll need a cite on how it misrepresents short people.

I’ve seen that athletes have their body mass overestimated; the elderly underestimated. I’ve seen no cites that these other groups – the short, the big-boned, etc. – are not accurately represented. That doesn’t mean they aren’t. It just means I need cites.

Personally, I still subscribe to the age old test of using multiple-skinfold measurements to come up with a “really” accurate body fat percentage.

I’m pretty sure that Dseid would concur with me on this - if you’re nudging over 20% body fat as a male, and 25% body fat as a female - time to change your lifestyle for the better. And why the gender difference? I’m told that females naturally require a 3-5% higher body fat percentage than males - especially approaching menopause - to aid with hormone production and levels etc.

Regardless, my point is this… the Body Mass Index is a pretty good indicator under most circumstances, except that it doesn’t allow for unusually heavy bone density, nor does it allow for unusually heavy muscle density - as exemplified in the aforementioned NFL linebackers etc.

I would contend that in upwards of 95% of cases, the BMI is a VERY sound indicator. The percentage of the population who have NFL levels of musculature, in reality, is very small. Also, as is the percentage of people who have extraordinarily heavy bone densitys.

However! Put a shitload of people through the skinfold tests who BELIEVE they have NFL levels of musculature, and/or ultra-heavy bone density and they’ll almost always be in for a very rude shock. Regardless of height… regardless of age… regardless of athletic prowess… without fail, only 1-2% of people over 30 on the BMI scale will NOT have body fat percentages well past the 20% mark.

Wow…you msut be my west coast twin, or something, cause I too am 5’11" and weight 177 (or pretty close to that.)

My skinniest at this hieght was probably a little below 130, 125 at the least. i was always a skinny kid, and the time when most peopel start to gain some weight (puberty) i was very active in x-country and track, so I would just burn off the calories. After four years of college, though, where I did no excersice, I went to a normal wegiht of about 160, and after a year out of college, I have put on some more pounds, and I can see where it is…it’s my gut. Thoguh I am starting to work out and diet to get rid of it and be back in the 160-165 range.


I’m 6’ 2.5" and weigh about 235. I run 3 miles 4 times a week and I strength train twice a week (I can bench about 350 lbs on a good day). Compared to the average 44 year old, I believe I am in excellent shape. Heck, compared to the average adult, I believe I am pretty fit.

I think I could still stand to lose about 10 or 15 pounds, but I just can’t make the lifestyle change to get it done, despite eating pretty well. According to the BMI, I am borderline obese. I hear what everyone is saying about how effective the BMI may or may not be for an individual. But according to the BMI I would need to lose 90 pounds before I would be considered underweight. I’d need to lose 45 lbs before I would be considered normal weight. So, for me at least, the BMI is silly and not very practical.

I agree with cricetus–at my low end of “normal” (145 pounds) I’d look like I was dying. The last time I weighed 145 lbs, I was a high school sophomore. So, the BMI may well serve a good purpose, but it doesn’t help me.

Do you have information on a good basic skinfold test? I’m 5’8", I have a BMI of 21, and yet a fat percentage of about 19% according to an electronic scale test. Perhaps it’s that a lot of my muscle mass has decreased this year, but I don’t think I could possibly have 26 pounds of fat on me.