Body Mass Index (BMI) Lunacy

There is a chart in the faculty/staff lounge above the medical office-style scale that says Body Mass Index (BMI) Chart. This chart claims to know how much you should weigh based on how tall you are, and claims the right to call you names if your body disagrees. I’ve always known that the chart was lunacy and those who promote it lunatics. When I started my weight loss program, I joked that I would have to lose forty pounds before I could be considered merely obese based on my BMI. I mean, we all know that muscle is denser and weighs more than fat and the BMI doesn’t take muscle into consideration.

The BMI is a statistical measure of body mass divided by the square of one’s height. Thus if this magic number is below 18.5, you are underweight; from 18.5-24.9, you are normal; from 25-29.9, overweight; 30-40 is obese; and over 40 is considered morbidly obese. My BMI is 32.4. My next immediate goal is to become merely overweight, thirteen pounds away. Assuming I want to carry it that far, for the next 27 pounds of weight loss, I will still be considered overweight. To be normal, I will have to revert to my college weight when I was sedentary, but weighed less. To be fair, I would have only had to be called overweight for the next 16 pounds prior to 1998 when the National Institutes of Health (NIH) changed the U.S. definition to match that of the World Health Organization (WHO). The NIH lowered the cutoff for overweight from a BMI of 27.8 to BMI 25. Overnight, 30 million Americans, went from healthy to overweight. I may be out of line, but I thought this kind of name calling should be based on scientific evidence of increased risk of disease. Am I the only one who has looked at the BMI and its guidelines and dismissed it as unrealistically out of reach? I’ll bet some have given up, choosing to remain fat.

Who is Responsible for This?

The BMI was first proposed by the Belgian scientist, Adolphe Quetelet between 1830 and 1850, as a statistical measure of the weights of populations, not individuals. The Centers for Disease Control says, “Calculating BMI is one of the best methods for population assessment of overweight and obesity. Because calculation requires only height and weight, it is inexpensive and easy to use for clinicians and for the general public. The use of BMI allows people to compare their own weight status to that of the general population.”

The BMI became popular in the 1980s because we started to notice that people in developed nations were become fatter. This was designed to be a measure of populations, not individuals, and that was why it was dusted off in the 80s.

How is it Used?

The BMI is used to screen for possible weight problems, not diagnose, but it is used prescriptively according to hospital protocols. Many hospitals require additional tests before performing some procedures if a person falls in the BMI obese category. A colleague related to me that her husband was subjected to unnecessary, and expensive, tests during a hospital visit because his muscled body fell into the obese category. Hospital personnel told her it was ridiculous, but needed to be done because of hospital rules.

The United States armed forces uses the BMI to assess fitness for military service. A student related to me the story of his drill sergeant who was a body builder with huge shoulders and a waspish waist and who had to get a special waiver before he was allowed in the military.

Why is this a problem? Body Types (Somatotypes) and the BMI

In the 1940s, psychologist William Sheldon studied the bodies of 4,000 men and devised a classification system based on body type (somatotype) in an attempt to discern temperaments based on his system. The temperament aspect of his theory has been largely discredited, but his classification system remains and it has implications for the BMI.

Sheldon classified people and their body types as, ectomorphs, who are lean, have little body fat, are not well-muscled, and have a trouble gaining weight; endomorphs, who have plenty of body fat and muscle, and gain weight easily; and, mesomorphs who are athletic, solid, muscular, and strong. They tend to eat what they want without gaining weight, and if they do, they lose it easily.

These different body types present challenges for the BMI because the ectomorph may have a deceptively low BMI that masks health risks, and the mesomorph has greater bone size and density as well as more muscle mass and may be classified as overweight. Few people are pure examples of these body types and may show blended characteristics. There are even people who are upper body ectomorphs and lower body endomorphs (pear-shaped), and those for whom the reverse is true (apple-shaped).

Still, the CDC considers the BMI “a reliable indicator of body fatness for most people” http://www.cdc.gov/nccdphp/dnpa/bmi/index.htm

What are the alternatives?

Other assessments such as skinfold thickness measurements, dietary evaluation, physical activity assessment, and family history can be used. My grandfather, who was thick but well-muscled even in old age, lived to be 98. The BMI would have considered him obese. Body fat can be measured by calipers (skinfold measurement), underwater weighing, bioelectrical impedance, dual-energy x-ray absorptiometry (DXA), and computerized tomography. My fitness center is considering the purchase of a bioelectrical impedance device. It’s simple and reliable, you just grip two metal rods and a small electrical current that measures your body fat is run through your body.

All of these assessments are more reliable than the BMI. The hip-waist ratio is even easier.

Hooray for the Waist-hip Ratio!

To determine your waist-hip ratio, you measure your hips at the widest part of your buttocks, then measure your waist at the smaller circumference of your natural waist, usually just above the belly button. To determine the ratio, divide your waist measurement by your hip measurement.

On the waist-hip measure from the University of Maryland Medical system waist-hip calculator, I came out at .958, considered a moderate risk. If I only lose ¼” in my waist, I go to low risk. That’s doable.

The ideal ratio for men is .9 and for women, .7. That is also considered by some the ideal for male and female beauty. If I lose 2 ¼“ in my waist, I can reach that ideal. Now, that’s a goal.

Here's my recap from yesterday.

Daily Dietary Recap-3/19/2007
Calories	Protein	Carbohydrates	Sodium	Fat	% Calories from Fat
1102.03	55.21 g	220.84 g	1257.23 mg	14.62 g	11.94%