Analysis of BMI

NoelFigart1

The expression BMI gets thrown out a lot lately, but it seems to me that very few people — either health professionals talking about weight, or people who talk about the fact that skinny is a lousy metric of health understand very well.

BMI means Body Mass Index. It’s a height/weight ratio where the weight in kilograms is divided by the square of height in meters. That’s it. It doesn’t measure what the weight is composed of (muscle, bone, adipose tissue, water bloating or anything). It’s just what you get when you step on a scale and then compute that number based on your height. Most adult male athletes would be considered overweight or obese by BMI standards. Clearly this is a measurement that leaves much to be desired.

It was developed somewhere between 1830 and 1850 by Adolphe Quetelet, a Belgian scientist who was trying to develop a discipline known as Social Physics. This was basically the study of Man by means of statistical measurements. Because many of his theories were not well thought of by his peers, the discipline of sociology supplanted it not long afterwards.

Quetelet did work in the public health sector, where his formula of BMI was applied to issues of health of the day. Thing is, these measurements were used to establish an average based on the 1840-1850 set of measurements he took. “Average” was then taken as a baseline for “acceptably healthy”.

Friends, barring cancer, almost anyone reading this is far healthier than the average person of the 19th century. Our mothers were better nourished while we were gestating. Our medical care — even if it was sub-standard, was better than was even available then. Losing a child has gone from something routine that most mothers faced to something unusual and unexpected. I have a friend who’d be facing death in childbirth in the next few weeks if it weren’t for obstetrical advances.

I wanna chuck the BMI for one reason: It’s bad science. It’s a statistical measurement based on environmental conditions that no longer exist compared to conditions we no longer find desirable. We’ve got better ways to measure health now. Let’s use ‘em.

paperpudding

I disagree.

BMI is a good guide when used in context. Yes elite athletes can have a higher than average BMI and this does not mean they are overweight - but in context of clinical picture, ie of seeing the patients body, it is obvious this is the reason for their reading.

For most of us, being somewhere within the healthy BMI range is a good guide as to whether we are a healthy weight.
Of course it is not the be all and end all of health markers - but that doesn't mean it is of no use either.

I'm not sure what obstetrics advances have to do with this.
And sure, people may be on average heavier than 100 years ago - but they are also on average taller.
How does this nullify BMI guides?

Patttience

Chuck it if you want. No one's forcing you to use it. But i'd say you are the one with a poor understanding of what it is and what it means. Its an average!!! Its a GUIDELINE that works for MOST people. You are probably one of the "most peopl" so in that case its likely that using it as a guideline works for you.

As to what you've said about "most adult male athletes", i wonder where you got that idea from?

The thing is BMI is not so useful for people at the extremes of the spectrum. That is well understood by the people who use it. That doesn't mean the whole concept is wrong.

But i've heard the view you put forward before, plenty of times. And it usually comes from people who are in denial about their weight and how it might be an indicator of poor health in the future.

NoelFigart1

I'm in favor of chucking it for body fat percentage. I think it's miles more accurate.

paperpudding

Yes, agreed, body fat percentage is also very useful.

But BMI is much easier to obtain, anyone at home or in a Dr's surgery can measure their height and weight and ascertain their BMI or the patient's BMI and thus get an easy and useful guide as to where they are sitting within healthy weight range.

Using BMI does not exclude the use of other health markers where available or relevant; it just gives a guide as to a heathy weight range.

dayone987

BMI can be calculated using a scale and a measuring tape. Body fat % is not easily done accurately.

LaurenAOK

paperpudding wrote: »

I disagree.
For most of us, being somewhere within the healthy BMI range is a good guide as to whether we are a healthy weight.
Of course it is not the be all and end all of health markers - but that doesn't mean it is of no use either.

I agree with this. The BMI scale has some flaws, which OP pointed out. But for most people, it's a generally good guide of what is or isn't a healthy weight. It's also a great place to start when setting weight loss goals. Some people have no idea how much they'd like to weigh, so they can start with picking a "healthy" number on the BMI scale and then adjust from there as they see their body change.

RubberBugggy

The Wikipedia entry on this scale has a good analysis - also on the fallacy of branding the "overweight" category as unhealthy - some studies say otherwisel