That BMI Thing

Ordinarily the WL blogosphere and I are just one big basket of snuggles, with deeply similar opinions on most topics. But there's one where I am apparently a renegade, which is the subject of Chunky Monkey Mamma's intriguing blog post over on Cranky Fitness (see my sidebar, sparing me the labor of making a link).

The opinion as expressed by the majority is that BMI is complete horseshit, and should not be measured at schools or conveyed to parents.

My thought is, it's all information, right? There's "Your hemoglobin is 9.3" and "I saw your husband clinching a redhead in the Denny's parking lot." Most people seem to feel that telling parents about their kid's BMI belongs in the latter camp, Information That Does More Harm Than Good.

Since it's my blog, this is my take on it. Pull up a chair.

What is BMI? It's just a fancy measure of weight versus height. We do it all the time when we look at someone's blog stats-- they weigh 173 pounds, for example. We look to see if they're 5'1, 5'8 or 6'1. If they're 6'1" and 173 pounds we stop reading their blog in annoyance because damn it, this isn't a proper WL blog, they're not even fat. See? BMI in action.

Most of us know that BMI doesn't measure body fat or muscle mass or athleticism. But it does take a stab at measuring. And the majority opinion seems to be saying that because it's not a perfect measure, we shouldn't take it or communicate it. They don't want to know, they don't want the kids to know, because it's upsetting.
The thing is-- if my doctor takes my fasting blood sugar and it's 113, it's very upsetting. I'll be worried and possibly even pissed at my doctor. Does that mean she shouldn't tell me? In my case, that measure had a very real and helpful impact on my behavior. It's possible, seeing objective evidence that a child's weight for height is unusually high, a parent might investigate further and possibly make some changes at home.

I'm not afraid of a number. Well, okay, some numbers, but not that one. BMI may be flawed (it is) but it is widely accepted, used by everything from the World Health Organization to research studies to insurance companies to Weight Watchers. Not forgetting weight loss bloggers. My kids tell me height and weight is taken privately: no one sees the letter except for the school nurse and the child's parents. Our letters actually take pains to describe the limitations of BMI. How the parents use that information is up to them, just like any other measure including grades, test scores, or vision screening results.

If this were any other number, like cholesterol or nearsightedness, we wouldn't be pitching fits over flaws in the system of measurement. It's because body weight is such a wretchedly loaded topic people don't want to know and some even get angry if a potential problem is mentioned. My doctor never said a word about my weight at any point, even with fasting blood sugars over 100. I'm sure she's been conditioned not to. Is she really doing me a favor? What do you think?


  1. I have no problem with BMI either except when it is misused and misunderstood... I think BMI often is. But then again I think the concept of weighing oneself is also often misunderstood and misused so I guess there really is no good way to measure our mass. Overall, I agree... it's all information use what you want and ignore the rest.

  2. I wonder if a lot of people have horrid childhood memories of standing in the nurse's office being weighed in front of peers. I sure do. The number is still burned in my head as she reports to the log-taker, "Gina Stephens: seventy-seven!" Maybe that's the fuel for the anger.

    I'm glad it's discrete. I think you make a great argument for the reported info. A lot of us parents are numbly trying to get through the day. Time goes by, and we don't realize how our actions (food choices, activity level) have affected our family. The BMI could be a wake-up call.

  3. I do not remember ever being weighed at school. My boys have not either...except my wrestler who must be weighed in before a match.

    A MUCH better measurement of body health is body fat percentage. But, that is trickier to measure than BMI. The thing with BMI is that someone with a low one might actually have too high of a percentage of fat (and be "skinny fat") and someone with a high one might be wicked-buff and muscled and have a super low body fat percentage. But...for the "average" joe/joanna...BMI is fine. I agree with you. It is just a number.

    The state sends me a letter when my kids pass or do not pass certain parts of the state exam in school.....I suppose if I got a letter about my kids' BMI it would be no different to me. If it was too high....I'd think about why it was high....and it it needed to come down....we'd come up with a plan to help them lower it. No biggie.

  4. more comment.....about the 6'3 178 hypothetical person....I DO like to read some blogs of those in the lower BMI range..because I want to know what they heck they do to get that weight and stay that weight...clearly...there might be something to learn from those skinny-butted folks.

  5. holy moly the music almost gave me a heart attack :)

    when Im back in the normal range Ill be back with my comment :)

  6. I think a lot of people get bent out of shape about BMI, some for good reasons, others maybe not so much. It is off for a few people, and when they start legislating by it, it can be a bad thing. I've heard stories of muscular guys who CAN NOT get to normal BMI, though have very low body fat%, thus losing benefits.

    The BMI isn't too far off for me, I'm about at 26, I will still be chubby at 25, maybe 22 (right in the middle) would be better, and I'll go for that after I re-evaluate at 25.

  7. I also don't ever remember being weighed at school.

    As far as BMI goes, I think the frustration in the blog world comes from those who consider it "the measurement" of whether you are overweight or not. It is too flawed to be used as the sole indicator. It is a tool, one that should be used along with other tools to determine if you are where you should be. I, for one, don't think it is complete bunk, but I think it is weak enough that it should be taken with a grain of salt. In my case I don't think it is the best measurement. Right now my BMI is 27.8. I don't think I am that overweight at this point. Nevertheless, I am not done yet, so maybe my mind will change over time.

  8. Schools seem to be crossing over more and more into healthcare. I don't remember ever being weighed at school. I don't really want my kids weighed at school, either. I go to the doctor for that. I don't want the school butting in telling me what my kids should be eating (our school does just that...fruits and veggies only for snacks at school) - I don't need a nanny.

    Wow - I'm cranky this morning. As for BMI and children, I can just look at my kid to know he's fine. I remember my brother being chunky as a tween, then shooting up to beanpole status as a teenager. Would BMI have been helpful then? No, his body was just changing.

    All that crank aside, I use BMI for myself as a tool. I desperately want to be in the normal range. Thankfully, my body type fits the mold and I should make it there in the next few months, I hope.

    Sorry for the diatribe.

  9. OMG I totally agree! (and hi!) I think "we" discount the BMI because we don't want to believe we really need to be that much thinner to be "normal." It's a sense of denial, really. I went from a BMI in April of 36.8 to my current 25.5. I'm looking forward to 4 more pounds lost to get into that 'normal range.' But will that be the right weight for me? NO. I plan on losing another 20 pounds. I want some "wiggle room" when I'm done. I believe in the BMI. I don't treat it as gospel, but I don't poo poo it, either. As a global community, baring 3rd World starvation, we are vastly overweight. And unhealthy because of it. We need to "own" that.

  10. Count me in the 'it's just another number' column. Useful, but not the whole story. :)

    Have an awesome weekend!

  11. I think we don't like BMI because it is a number. It's a hard fast number that may or may not make us happy. I think that like you said, it's a useful piece of information, although certainly not a perfect one.

    Great post!


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