Dr. J on revisiting the Body Mass Index
Contributor: “Dr. J”Dr. J offers his irreverent, slightly irrelevant, but possibly useful opinions on health and fitness. A Florida surgeon and fitness freak with a black belt in karate, he runs 50 miles a week and flies a Cherokee Arrow 200.
Every time BMI (body mass index) is mentioned, it seems there is always a flurry of responses adamantly insisting how incorrect and useless it is! Almost to a letter, the argument is that it does not correctly identify the person’s appearance.
The BMI is not meant to be a beauty contest, and for what it’s worth, the beauty-on-the-inside concept was discussed in an earlier column, when I talked to an anatomist friend about his experiences with our innards!
I can certainly understand why someone wouldn’t want their doctor to say, “You are fat!” I do hope your doctor would tell you, “You are at an unhealthy weight,” if by the standards he or she was taught, you were. Please realize that your doctor is not saying that you look bad. Hopefully, unless they are a cosmetic surgeon, their focus is on your health.
Why BMI isn’t so bad
As far as BMI goes, I really don’t understand the hostility toward it. Of course, it isn’t perfect as a predictor of health and fitness. Even if you were to measure total body fat, abdominal body fat and waist to hip ratio, and combine it with a genetic analysis, it still would not be perfect. However, I do think the BMI is accurate enough. It doesn’t state that you should weigh some particular exact weight. The BMI gives a 6.5-point span, which gives you a normal range of about 35 pounds for your particular height.
I think the problem that arises with individuals who oppose the BMI is that they misunderstand two factors.
The BMI has value related to health, disease, disabilities, and death
All of the research and studies of rising disease, disabilities and death rates attributed to being overweight or obese use the BMI to categorize the patients with diseases into underweight, normal, overweight and obese categories. If BMI is wrong, how do you account for these accurate results?
The BMI and the data related to the BMI are group statistics
They relate to the larger group, not the individual. These values give predictions for the overall group. Whether you will be the exception to these statistics is the gamble you may or may not choose to take. Just know, if you choose to ignore them, according to the data, the odds are not in your favor.
The data on health, disease, disabilities and death
- An estimated 300,000 deaths per year may be attributable to obesity.
- The risk of death rises with increasing weight.
- Even moderate weight excess (10 to 20 pounds for a person of average height) increases the risk of death, particularly among adults aged 30 to 64 years.
- Individuals who are obese (BMI greater than 30) have a 50 percent to 100 percent increased risk of premature death from all causes, compared to individuals with a healthy weight.
The following summary of the health consequences of being overweight or obese comes from the Office of Public Health and Science and the U.S. Department of Health and Human Services.
Negative effects of being overweight or obese:
- Higher rates of premature death
- Increased incidence of heart disease
- Increased incidence of diabetes
- Increased rates of cancer
- Increased incidence of breathing problems such as sleep apnea and asthma
- Increased incidence of arthritis
- Increased incidence of reproductive complications during pregnancy, in both the mother and the offspring,
irregular menstrual cycles and infertility - Increased rates of gall bladder disease, incontinence, increased surgical risk and depression
The Body Medical Index
Perhaps, if the BMI was renamed to be defined as the “Body Medical Index,” and rather than a physical description, it was divided into healthy, less healthy and much less healthy, it would be a more satisfactory index to its critics! Unfortunately, for the vast majority of individuals, where they were placed in the index would remain the same.
Like the popular belief about the ostrich, we can bury our heads in the sand in relation to our BMI, be it body mass or medical index, but that will not change things. Actually, contrary to popular belief, ostriches do not bury their heads in the sand. This myth likely began with Pliny the elder (A.D. 23-79), who wrote that ostriches “imagine, when they have thrust their head and neck into a bush, that the whole of their body is concealed.”
Fascinating!
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Vera!
Keep doing what you are doing, and I’m sure you will be fine. As I said, although the BMI has sharp boundaries, for the most part, life does not.
FredZ!
I appreciate your comment! Please understand when I tell you that, and I’m guessing that you are relatively young, as you get older, 6’2, 270, will cause problems for you. I am acquainted with an ex-gator nose tackle. He played at 6’2′, 310! Now he is in law enforcement at a solid 220. Personally, I think he’s better off like this.
I’m self-employed, in perfect health, 6’2″, 270 pounds, run an 8 minute mile, and can bench 400 pounds — and I am un-insurable in the state of Colorado. I’ve been automatically rejected by 6 different insurers solely because of BMI. I’m currently uninsured but am going to have to pay for the the same State-provided high-risk insurance that unemployed people with terminal cancer have to use. You can probably guess my opinion on the accuracy and fairness of BMI.
While I feel that BMI can be useful. I personally HATE IT for myself. I’m 5’4″ and I weigh 150. I’m a solid size 8. I work out and watch my what I eat, and I really don’t want to be much thinner (maybe 5 lbs or so), yet the stupid BMI says that at 26, I’m overweight.
Tricia!
:-) Of course the delineations between the BMI categories are very sharp on the Index, but we all know that the real boundaries are blurry as one goes from one into the next. I do agree with you that our bodies do have the final word on health. However, as I’ve said, the BMI does accurately predict future problems, and if one is presently unhealthy, looking at the BMI and body composition for areas of potential health improvement is prudent.
Thank you for commenting on the column!
Excellent points. I have to admit in a recent post I said, “I don’t need a BMI chart to tell me I’m healthy, my body tells me I’m healthy.” Yeah…I’m one pound off from being in the “healthy weight” category and darn it that irks me. Check back next week when that pound is gone and I wonder if I’ll suddenly be a BMI advocate. :)
Vered!
That’s the way I feel!
Sagan!
As I said in the comments, I feel the BMI is accurately predictive of future health problems, as the research shows. If your young super athlete friend stays obese/morbidly obese as she gets older, she will not be laughing.
I think you’ve made an excellent point that it’s good ENOUGH. Yes. There isn’t any possible way to have a universal system because we’re all different, but the BMI is a good guideline. Although I do find it pretty funny that my super athletic friend is considered obese- or it might be morbidly obese- by the BMI standards, even though she’s clearly very healthy. Hehe.
I know many rebel against BMI but I agree that it’s a good general guideline. If you are very overweight obese according to the BMI guidelines, then no doubt you need to change your habits!
Crabby!
Good observations and advice! You know, I’ve never met anyone in the normal BMI range that dislikes the measurement :-)
What a great discussion! I thought you were brave, indeed, Dr. J, for defending a measuring tool that so many dislike.
Personally, I think the percentage of body fat is more helpful than a weight to height ratio, but no single measure is going to tell the whole story no matter what it is. I think everyone, regardless of weight, should be focusing on eating healthy food, keeping portions reasonable, getting proper exercise, and taking care of themselves. So I wouldn’t want to stigmatize a muscular or big-boned person who’s doing all the right things with a number that doesn’t reflect their real health risks.
Great topic and so many good points on both sides!
Sahar!
I saw an ostrich while running a few months ago! In that case, I was the one considering hiding in the bush!
Carla!
Even I am not a fan of the BMI for young children. Your daughter is adorable!
Charlotte!
Better the BMI falling apart for the individual, then the individual falling apart for the BMI!
You and I need to collaborate on developing the BDI!
I totally agree that the BMI is useful in comparing and analyzing groups but like Ruth and Miz it tends to fall apart on an individual level, esp. in regards to muscle mass. I’m not saying that people shouldn’t know their BMI or that doctors shouldn’t use it as an analytical tool – I’m just saying it shouldn’t be the *only* measure of good health.
PS> Your post guilted me into looking up my current BMI to motivate me to avoid the gummy worms today. How surprised was I to find that I’m already a 21?? Maybe I have less baby weight to lose than I thought… Is there a body dysmorphic index? ;)
Im torn on this one….I COME OUT HIGHHIGH on the BMI but am aware enough to know why.
My daughter is pretty “big” as well according to the doctors but doesnt yet have the ability to realize that lots of it is muscle.
The one thing that always comes up about BMI is that it doesn’t account for muscle mass. But I agree that even though it is not perfect, it is accurate enough. Now, about this whole ostrich thing – who knew???
Roy!
Maybe looking at one’s medical bills for the year would be a good measurement?
POD!
I bow to Buddha.
Beth!
I tend to think of a person’s BMI as an indicator of potential future health issues, as all the research supports, but if you don’t like it as a mathematician, that’s fine.
Count me in the anti-BMI crowd! As a math major, I find it annoying that numbers that aren’t meaningful as is (which is why we don’t use height and weight tables anymore) are somehow more useful when you square height and convert the ratio of that to weight in metric form. Ugh.
And how’s this for taking a stand: Keith Devlin of NPR wrote an article for them last summer on why the BMI is bogus:
http://www.npr.org/templates/story/story.php?storyId=106268439
I’ve no objection for using BMI as a marker (much like weight or waist measurement). But I’m with Ruth … there are better measures of health!
I can’t even spell BMI.
For the greater good of the American people, I accept your thesis Dr. J, thought I don’t agree with it all the time. I also accept my place as being obese; and simultaneously having 11% body fat (under water).
I hope though, better means of measuring are explored. As a self-employed business man, this could become a factor for me purchasing health insurance for myself. It currently isn’t a factor, but as well all know, the insurance game may be changing.
John!
That’s why I like the art of medicine more than the science :-)
Blake!
Nice to hear from you!
Ruth!
It’s OK, if you don’t want a BMI, don’t have one :-)
Diane!
Try out my idea of a Body Medical Index, and see how they feel about that.
Merry!
Thank you! Working to be as healthy as we can is the best way to go!
Jody!
I’m leaning more and more toward the Body Medical Index! If we are not in the healthy category, it would be wise to improve all the factors we can.
Hey Brandon!
I agree, the BMI is useful to get people who need it to pay attention. Like your plane’s computer, when it says you are too low, but you are actually landing, staying the course is the better plan :-)
Hey Dr. J,
my captain for the month and I have debated BMI at length (you think we are just sitting up there monitoring the instruments? ;-)) and his conclusion is an interesting one.
With the epidemic that is obesity, you have to give people a basic benchmark. Many people out there that are TRULY obese have no idea that they are. They think they are healthy. Without being able to calculate body fat (which can vary 3-6 percent) or other things like blood pressure, cholesterol, etc. a person that has no idea where to turn to measure their health can look at BMI as a basic benchmark.
For me, I am overweight by BMI standards. That’s fine. I accept that it’s not the perfect system. I also have a resting pulse rate of 58, a body fat of roughly 15%, and as far as I know, normal cholesterol. My blood pressure is slightly high, but I have been told by numerous doctors that my family history is a factor in that as well as my job.
BMI can serve a purpose. Is it a foolproof system? Of course not. But I think it has its place in our society.
Merry, Dr. J., et. al.,
I think what makes the most sense to me is a Health at Every Size approach. The focus should be on BEHAVIORS (ie, nutritional choices, portion sizes, exercise, meditation, etc.) and not CHARACTERISTICS (weight, etc.).
Characteristics can be indicative of issues that need to be addressed, but are not entirely in our power to control. But, we can always choose healthier behaviors, and these will benefit us regardless of what the #s say. And, when we make healthy choices and address our health issues, the numbers settle where they are meant to be.
And Merry, hope your Thanksgiving was great too, and that you’re recovering from your (minor) injuries. ;-)
I like your post Dr. J because it points out all the negative effects of being overweight. Yes, BMI is not a perfect science but it is a start & many people like to deny the truth when it comes to weight & health, unfortunately.
For me, it does not put me in an unhealthy group but it does measure me higher than I actually am due to the fact that I am heavier for my height due to my muscle mass. BUT, I know this so I take that into account. Those that are athletes know this. For the average person, it is a good start & for some, an eye opener they don’t want to see….. but it should be incentive to make changes!
Diane, maybe people have an instinctive dislike of the BMI idea because it makes them think of themselves as just a number? I hate to think of my BMI because the answer is depressing. (For now.)
The BMI can be used as a starting point. Most of time, when someone mentions the example of a healthy person with an unhealthy BMI, they’re referring to an athlete or someone similarly on the extremes of the curve. BMI is a general aid, not a specific, invariably correct, tool.
While I hate to disagree with Ruth, I think that whether the excess weight was caused by a disease or the disease was caused by excess weight (e.g. insulin resistance) either way you’re screwed, so does it matter which one came first? (Yes, which came first would change the approach to curing it, but not change the /need/ to fix the problem.) Even if the weight gain wasn’t the underlying cause, it’s going to create more problems on top of the initial problem.
A BMI number outside of the norm could be useful as a potential red flag, which would cause a doctor to look further. As Ruth points out, they could then go on to check other things such as body fat %.
And I hope you /both/ had a great Thanksgiving :)
Whenever I mention BMI on my blog or in my weight loss class I always get some flak. For whatever reason, people just don’t like it. I wonder if part of it is our natural tendency to reject those things that we don’t like.
I had a BMI of 43.8 at one point. Definitely not healthy. I think I would have been in the camp of “it’s not accurate” because I would have liked to think that any measurement that classifed me as morbidly obese could possibly be wrong.
That being said, I do understand why people like your previous commenter oppose the BMI. There are always folks who don’t fit statistics, and for those people, it doesn’t work.
Hello Dr. J.,
I respectfully disagree that the BMI is a useful tool for assessing health.
I understand that it may have value as a statistical tool. However, among its many shortcomings:
1) It only takes into account weight and height. Even though it provides a range, it doesn’t take into account race, bone-density and muscle mass, all of which effect weight.
2) Many healthy people are statistical outliers in one or 2 measures. (As an example, my pulse tends toward the rapid side, even when I am relaxed, working out a lot, etc. By itself, no big deal since my cholesterol, blood pressure, etc., are all good, and I am healthy.)
3) Even if BMI were an accurate measure of a healthy body composition in all instances, correlation doesn’t prove causation. There are lots of factors that might cause weight gain, such as certain medications, thyroid problems, type II diabetes, etc. In other words, many times, weight gain is the chicken, not the egg. With the focus on BMI as a measure of health, there is an unfortunate tendency to think that losing weight is a magical cure for health issues rather than treating underlying issues that might cause weight gain.
BTW, my sister, a doctor, agrees more with you than with me, and I am not a doctor, but I do think that body fat %, waist to hip ratio and other measures are better indicators of health than BMI, which I see as mostly a statistical tool.
Thanks for letting me say my piece.
Ruth
PS. Hope you had a great Thanksgiving!
Great article. I agree that BMI isn’t perfect, but it is a good guide. Eye opening to see all the negative consequences of being overweight or obese… i know most of them but interesting to see a lot of them right there. Can’t argue with those. thanks!
Hey Dr. J,
When I used to sell life insurance, the company used every statistical tool at its disposal to figure out risk. Anything that could be measured and then studied contributed to the actuarial tables.
As is said in business, if you cannot measure it, you cannot improve it.