Saturday, February 6, 2016

Relying on BMI as a health metric is a bad idea

While it may be generally true that an exceedingly high body-mass index score suggests poor health, it is not always true, and a UCLA study, according to an LA Times story, suggests relying on BMI as a health metric is a bad idea:

“A new study from UCLA finds that some 54 million Americans who are labeled as obese or overweight according to their body mass index are, when you take a closer look, actually healthy. The findings, published in the International Journal of Obesity, reveal that employers could potentially saddle people with unfairly high health insurance costs based on a deeply flawed measure of actual health.”

The article explains BMI:

“Body mass index is calculated by dividing a person’s weight in kilograms by the square of the person’s height in meters. According to the Centers for Disease Control and Prevention, a “healthy” BMI is 18.5-24.9, an overweight BMI is 25-29.9 and an obese BMI is 30 or higher.”

The problem with using that number for “health” is that it can mask serious ailments — like high blood pressure — in people with a low BMI and wrongly presume that individuals who are overweight or obese also have those sorts of ailments. They may be true in general, but wrong in a lot of specific cases. BMI is, the research suggests, too crude a measure to apply to any one individual.

“Researchers have begun to suspect that people with so-called “healthy” BMIs can be very unhealthy, and those with high BMIs can actually be in very good shape.”

The inaccuracy of BMI on an individual basis might have actual financial consequences:

“… the U.S. Equal Employment Opportunity Commission recently proposed rules that would allow employers to penalize employees for up to 30% of their health insurance costs if they don’t meet 24 health criteria — which include meeting a specific BMI. If body mass index doesn’t accurately reflect health, then those with high BMIs potentially could be overcharged for no reason.”

After examining data from more than 40,000 individuals, here is what was discovered:

“(The UCLA researchers) found that nearly half (47.4%) of overweight people and 29% of obese people were, from a metabolic standpoint, quite healthy. On the flip side, more than 30% of individuals with “normal” weights were metabolically unhealthy.” 

My own belief is that a better, or maybe just a less crude measure of body size is a person’s waist-to-height ratio. Generally, the number of inches around your waist (at its widest point) should be under half the number of inches you are tall. 

In my case, I weigh 200 pounds, my waist is 33.5 inches and I am 74 inches tall. So my waist-to-height ratio is .453. That is in the healthy category. A man who is my same height and weight, but has a 39 inch waist is overweight, because his waist-to-height ratio is .527. Yet the two of us would have the same BMI score, and that would be misleading.

The basic idea behind waist-to-height ratio is that it does not matter so much how much you weigh relative to your height. What matters is where you are carrying that weight, and to that extent whether your weight is muscular or lipidic. 

From WebMD: 

“This visceral fat in your middle makes toxins that affect the way your body works, says Samuel Dagogo-Jack, MD, president of the American Diabetes Association. Among them are chemicals called cytokines that boost your chances of heart disease and make your body less sensitive to insulin, which can bring on diabetes.

“Cytokines also cause inflammation, which can lead to certain cancers, says Eric Jacobs, PhD, a researcher at the American Cancer Society. In recent years, he says, scientists have uncovered links between belly fat and cancers of the colon, esophagus, and pancreas.”

If you are slim all over but fat in your gut, you are probably much less healthy than a person who is the same height and weight but carries his weight in thick, muscular legs, butt, back, chest and arms with a slim waist. 

No comments: