Bellies and Fatheads

July 20th, 2009 by Harrumpher Leave a reply »

Talk to someone else about the glories of the BMI. I know that the near-universal body mass index instead might stand for bull measurement for idiots.

A splendid explanatory piece on it appears in Slate.  Jeremy Singer-Vine’s Why doctors won’t stop using an outdated measure for obesity. details how BMI came into being and particularly how it come to substitute for any semblance of science and observation by so many doctors and other medical professionals.

I won’t go into those details. However, the punchline is that it is absurd to use BMI in individual cases, be they a school child or an adult. BMI can be a pretty good societal indicator of the general fatness level of the population, but folds immediately into irrelevance for any given person.

Dividing someone’s weight by the square of his height for large groups is a fine general indicator. The variations in somatotypes, as well as percentage of heavy muscle and light fat, produce comical BMI judgments. Many athletes in top condition come out as obese in BMI. Many trim-looking sedentary sorts measure healthy by BMI but have low muscularity and organs surrounded with unhealthy fat.

Yet, as the Slate piece so well illustrates, we love simple and quick answers…that particularly includes primary care physicians. Woe to any of us who try to lose or gain weight to match a height/weight chart or the slight variation that is BMI. You can sicken yourself by either flabbing up or having your body eat away excellent muscle mass to make the numbers.

Yet it is easy to understand why a doctor or nurse would fall back on a BMI for a patient. How tall and how much you weigh is easy and the scale is likely in the examining room. You can churn out a bunch of patients quickly, make your quota and seem to have done some science. That’s all without wasting any time with meaningful measurements or observation or diagnosis.

Truth be told, most medical professionals are far from nutritional experts. Their sparse training in the field is comparable to a minister’s business work in divinity school. They learn on their own or not at all. In fact, those of us who read newspapers and pop magazines stand a good chance of knowing more about the field than someone who has to keep up on all the diseases and the pharmacopoeia of symptom treating/non-curing drugs available.

Doctors should certainly know more about diet, exercise and body fat than they do. Yet, they are under tremendous pressure to bill visits and not to take extra time with each patient.

It makes more sense to me for them to pay attention to patients’ bodies when they palpate or listen to hearts and lungs. Their trained eyes and hands can get a fair sense of fat levels, fairer than a BMI.

body fat reading

Moreover, every examining room should have a body-fat monitor (a.k.a. body-composition analyzer). Percent of body fat is vastly more meaningful and useful as a diagnostic tool than BMI. Plus, the monitors as used in fitness centers, plain old Y’s and by physical therapists are inexpensive, in the range of a stethoscope and cheaper than the ubiquitous scale.

A long time ago, I got a scale that measures weight as accurately as my wife’s balance beam model. It has a body-fat function at the same time, customized for your age, height and build. Fortunately, I also had bought a hand-held fat monitor too.

When I got the titanium rod in my leg, it messed up the fat measurement from the scale, which sends electrical pulses up the legs. Apparently 14.2 inches of metal in the leg disrupts that process.

The hand-held monitor provides results in the same range as the old caliper system.  Importantly, measuring those pinches of fat in numerous places is very time consuming, more subjective, and only provides a range after all the trouble. Whether the fancy ($50 to $100) or less so ($30 to $50), these body composition analyzers are pretty accurate, more consistent than calipers, and give readouts in seconds. As with a scale, using the same monitor at the same time of day in the same way is the most accurate way to go.

Slate‘s article headlines with the question of how BMI stays popular with docs when it is pretty much meaningless for individuals. The simplest way to describe it is that it is down-and-dirty easy. It’s fast and comes with a spurious air of authority. Doctor and patient alike can pretend it’s real science.

Meanwhile come physical-exam time, if your doctor won’t give you a body composition analysis or is lazy enough to diagnose your condition using BMI, speak up.

You should own a BF scale or monitor anyway. You can show up at the next physical with a printout of your readings for the preceding months. It can only benefit you and other patients for the doctor to know that you expect a real and meaningful measurement before heading home to tweak your body and stay healthy.

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2 Responses

  1. Uncle says:

    BMI stays popular for the same reason the equally flawed Met Life measurements stayed popular before it: it’s there and it’s easy. Perhaps if we can ever break the back of fee for service, we can get physicians to show more depth.

    Interesting about the rod. Can you also pick up radio signals with it?

  2. Harrumpher says:

    For the rod (Expert Nail by trade name), I am not sure whether I”m relieved that the metal detectors have let me pass through without triggering because it is non-ferrous or missing the excitement and stories. I don’t understand why it should disrupt the flow of electricity though for the BF scale function. It makes me wonder whether the juice shoots up the marrow, which is now missing and replaced with solid metal. Harrumph!

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