Archive for the ‘Health’ Category


March 27, 2010

I already wrote, in a post last June, about how the “socialist” charges leveled at Barack Obama miss the mark. The “socialist” label lately applied to the new health-care law reminds me of the first session of the West German Bundestag, which I heard broadcast live on the radio in Germany in 1948. As some right-wing deputy was blabbering Sozialismus, the leader of the Social Democratic Party, Kurt Schumacher, rejoined with Was wissen Sie vom Sozialismus? Buchstabieren Sie nur einmal das Wort! (What do you know about socialism? Let me hear you spell the word!)

In fact, the health-care law is about as capitalistic as any such legislation can be. By comparison — but only by comparison — Medicare, Medicaid and Social Security would fill a Marxist with joy. Of course, I don’t mean the dog-eat-dog, free-market capitalism of Adam Smith or Ayn Rand, a form that Wall Street said good-bye to many years ago, but modern capitalism, with corporations getting heaps of subsidies and a modicum of regulation from the government. That, plus tax incentives, health savings accounts (in private banks, of course) and the like — where in the world is the socialism?

I understand that Rush Limbaugh, the leading hurler of the “socialism” epithet, has gone back on his vow to move to Costa Rica if the law were to pass. I don’t think much of Rush Limbaugh, but I never thought of him as an ignoramus, and yet how did he not know that a civilized country like Costa Rica would have nationalized health care?

Here’s another personal experience. Unlike Spain, where government-run hospitals and clinics are open to tourists (as I found out from the excellent treatment that my wife received in a little mountain village after arriving from Morocco with an intestinal disorder), in Costa Rica such services are only for permanent residents. And so, when I found myself with wax-clogged ears the day before I was to fly  back to the US, I discovered that all the doctors in the town where I was staying were working, on that day, at the public health center, and that without a national ID card I would not be attended there. All the doctors, that is, except one. I was given directions (Costa Ricans don’t use street addresses) to his office, was seen by him, and then referred back to the public health center, where I was to ask a nurse named Doña Carmen for a lavage. When I protested that I wouldn’t be served at the center, he said, “Just ask for Doña Carmen. She’s my wife.”

Are we 2-D? BMI!

December 2, 2007

Once again, a rash of media articles about obesity in the United States has broken out. And once again, the obesity statistics are defined in terms of BMI. Here is an example, from

To determine which cities were the most obese, we looked at 2006 data on body mass index, or BMI, collected by the Centers for Disease Control’s Behavioral Risk Factor Surveillance System, which conducts phone interviews with residents of metropolitan areas about health issues, including obesity, diabetes and exercise.

In this case, participants report their height and weight, which survey analysts use to calculate a BMI. Those with a BMI between 18.5 and 24.9 are considered at a healthy weight, those with a BMI between 25 and 29.9 are considered overweight, and those with a BMI of 30 or higher are considered obese. About 32% of the nation is obese, according to the Centers for Disease Control; Memphis ranked above the national average at 34%

Never mind that the city that ranked third in obesity, Nashville, turned up among the 25 “fittest” (as opposed to “fattest”) in a different survey, this one by Men’s Fitness (and, as far as I can tell, not based on BMI). I am not interested in the results, only in the use of BMI. And, what’s more, after entering “obesity BMI” in a Yahoo news search, not one of the first ten articles that I clicked on included an actual definition of BMI.

The BMI, or body-mass index, is defined very simply as a person’s weight (in kilograms) divided by height (in meters) squared. Thus, since I weigh 66 kg (145 lb.) and stand 1.71 m (about 5 ft 7½ in), my BMI is 66÷1.71² ≈ 22.5.

Now anyone with any familiarity with physical science will recognize a quantity defined as force (such as weight) divided by length squared (or area) as representing pressure or stress. For example, for people of different sizes but with similar body proportions, the area of any portion of their body surface – for example, the portion that is in contact with a chair on which they may be sitting – will be proportional to the square of the height. If the chair bears a person’s full weight, then the average pressure on the chair’s seat, equal to the weight divided by the contact area, will be proportional to that person’s BMI.

It is precisely for this purpose – the design of office chairs – that the quantity now known as BMI was invented by the nineteenth-century Belgian mathematician Adolphe Quetelet.

But human bodies are three-dimensional, not two-dimensional. For people of different stature but similar geometric proportions, the body volume is proportional to the cube, not the square, of the height. And if the proportions of the various constituents of body mass (bone, muscle, fat etc.) are similar, then the weight is proportional to the volume, and consequently to the cube of the height. Consequently, what people who are geometrically and physiologically similar have in common is the weight divided by the height cubed, not squared.

What this means is that people with the same build will have a higher BMI if they are taller and a lower BMI if they are shorter. It has already been noted that very tall people who are quite fit — for example, professional basketball players — have BMI values that would rank them as overweight. Thus, an NBA guard who is two meters (about 6 ft 7 in) tall and who has the same build as I do would weigh 66×(2.0÷1.71)3 ≈ 106 kg (232 lbs) and his BMI would be 26.4, in the “overweight” range.

It has also been remarked that in populations that, on the average, are significantly shorter than European (or European-descended) ones, a lower overweight threshold is necessary. For Southeast Asians, for example, it’s 23 (as in this document from Singapore). Were the body types the same, this would be consistent with average height being about 8% less. In fact, the average adult height in China, for example, is 6–7% less than the average of white Americans. But the body types are in fact different (for example, the waist-hip ratio of Chinese men is 0.87 while that of white Americans is 0.98, as given here).

I have no doubt that if an index were defined on the basis of weight divided by height cubed, the discrepancies would become negligible.