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BMI -Bull Manure Index?

casebro

Penultimate Amazing
casebro
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Jun 14, 2005
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This link is to a study done that reports that the overweight live the longest, BMI up to 34?

http://xa.yimg.com/kq/groups/9196911/56873634/name/oby2009191a.pdf

And my understanding of the BMI system is that it is merely a modernized formula for the Met Life Tables. Said tables had a simple formula, too pat for me: For women, 60" tall, 100 pounds, add five pounds per inch. For men, 60" tall, start at 125". add the same five pounds per inch. I guess I never believed that Met Live really did much research. Their chart is just too simple.

Now the Kaiser study linked above, and others, prove them wrong.

So I just had a thought. Why hegth/weight at all? Perhaps there is a better metric? Not merely pounds per inch, Imperial or metric.

Perhaps the Kaiser statisticians should go back over their data. Look for height based variables, as well as ht/wt?

I'm thinking that everything might become even more clear, using a cube of height? Hey, If I'm 10% taller, and in proportion, that makes me 10% wider too, 10% thicker too, so should I weigh 133% of standard?

Or maybe the formula would be the inverse, cubed? .9 times .9 times .9, maybe somebody 10% taller ought to weigh 72% of standard? Or maybe the square of the inverse?

20 years ago I heard that height is about the #3 risk factor in C.A.D. But nobody says I should get my femurs cut down 2". ;) So maybe the taller you are, the skinnier? or would it be fatter? But no sense that the BMI should not shift some.
 
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casebro said:
This link is to a study done that reports that the overweight live the longest, BMI up to 34?

http://xa.yimg.com/kq/groups/9196911/56873634/name/oby2009191a.pdf

And my understanding of the BMI system is that it is merely a modernized formula for the Met Life Tables.
Click to expand...


What broscience web site did you get that "fact" from? BMI pre-dated the inception of the Metropolitan Life Insurance Company by about 20 years.


So I just had a thought. Why hegth/weight at all? Perhaps there is a better metric? Not merely pounds per inch, Imperial or metric.
Click to expand...


Do you really think that you're such a genius that you're the first person to have had that thought? Simple measures that correlate with body fatness have been the subject of study for 150 years. Do a little bit of research, for Christ sake.
 
Food for thought

Abstract
BACKGROUND:
Body mass index (BMI) is the most widely used measure to diagnose obesity. However, the accuracy of BMI in detecting excess body adiposity in the adult general population is largely unknown.
METHODS:

A cross-sectional design of 13 601 subjects (age 20-79.9 years; 49% men) from the Third National Health and Nutrition Examination Survey. Bioelectrical impedance analysis was used to estimate body fat percent (BF%). We assessed the diagnostic performance of BMI using the World Health Organization reference standard for obesity of BF%>25% in men and>35% in women. We tested the correlation between BMI and both BF% and lean mass by sex and age groups adjusted for race.
RESULTS:

BMI-defined obesity (> or =30 kg m(-2)) was present in 19.1% of men and 24.7% of women, while BF%-defined obesity was present in 43.9% of men and 52.3% of women. A BMI> or =30 had a high specificity (men=95%, 95% confidence interval (CI), 94-96 and women=99%, 95% CI, 98-100), but a poor sensitivity (men=36%, 95% CI, 35-37 and women=49%, 95% CI, 48-50) to detect BF%-defined obesity. The diagnostic performance of BMI diminished as age increased. In men, BMI had a better correlation with lean mass than with BF%, while in women BMI correlated better with BF% than with lean mass. However, in the intermediate range of BMI (25-29.9 kg m(-2)), BMI failed to discriminate between BF% and lean mass in both sexes.

CONCLUSIONS:
The accuracy of BMI in diagnosing obesity is limited, particularly for individuals in the intermediate BMI ranges, in men and in the elderly. A BMI cutoff of> or =30 kg m(-2) has good specificity but misses more than half of people with excess fat. These results may help to explain the unexpected better survival in overweight/mild obese patients.
http://www.ncbi.nlm.nih.gov/pubmed/18283284
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bold mine
 
The mystery to me is that a high jumper and a rugby player might be exactly the same height and both be totally lean and super-fit, yet the latter could be reckoned 'overweight' according to the BMI calculations. So, yes, they do strike me as very simplistic.
 
Doesn't a simple weight measurement correlate better with obesity related ill health? I seem to remember reading about that a while back. It makes sense, since abdominal fat is the most dangerous.
 
Professor Yaffle said:
Doesn't a simple weight measurement correlate better with obesity related ill health? I seem to remember reading about that a while back. It makes sense, since abdominal fat is the most dangerous.
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I'm assuming you mean waist? I would think it would, but not sure.

Neck-to-waist measurements ratios are commonly used to estimate fat percentage, but I don't know how those correlate either.
 
Kopji's quote is of some service. But it is comparing the finding of a preconceived weight as obesity by two methods. But is there a robust study backing the body fat/risk connection, and defining obesity as a fat percentage related risk factor?

In 1999, my HMO taught that the 5 highest risk factors were- age, heritability, weight, cholesterol, and height. Since then, we've dropped age and height as not being 'controllable', and heritability has been downgraded. I guess if your parents were fat, and your grandparents were fat, and all died of heart disease, now it's blamed on the fat, NOT heritability. Current prevention concentrates on BMI and lipids.

The study linked in the OP should change some thinking. It was done in 2009, and hasn't changed anything yet. We still use the term 'overweight' to describe the best longevity range. I wish the studiers posted their results as a line graph, so we could see the slopes. A point where the slope suddenly increases would be a good place to draw a line, the place where RR starts a sudden climb. And I doubt there is one. I think it's drawn at a pretty arbitrary point now, BMI 34.9 is OK, but 35 is OM FSM!! You are going to DIE!!!

I'm also confident that science isn't done with the issue yet. The K2/Calcium connection looks like it may be a huge leap forward. Arterial calcification is supposed to be the strongest risk factor for secondary heart attacks. Perhaps plaque develops as a result of calcification, fixing that may be right at the root of the problem. I think it takes a CT, not just a drop of blood, to check it.
 
The wiki on 'atherosclerosis' lists obesity 12th, in the section of "Lesser or uncertain".
 
casebro said:
The wiki on 'atherosclerosis' lists obesity 12th, in the section of "Lesser or uncertain".
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It may be more related to long stretches of inactivity than either obesity or sedentary life per se. There was that disturbing study that seemed to show fit people who exercised than sat on the sofa for 6 hours straight had little or no edge over couch potatoes who came home from work and plunked down.

I assume follow up studies are under way.
 
Just because BMI isn't the end-all be-all in terms of health indicators doesn't mean you aren't fat. I mean isn't that what most people complaining about BMI are really trying to convince themselves of?
 
Then there was this recent story:

People can be obese yet physically healthy and fit and at no greater risk of heart disease or cancer than normal weight people, say researchers.

The key is being "metabolically fit", meaning no high blood pressure, cholesterol or raised blood sugar, and exercising, according to experts.

Looking at data from over 43,000 US people they found that being overweight per se did not pose a big health risk.

The results are published in the European Heart Journal.

In the study at the University of South Carolina, more than a third of the participants were obese.

Of these 18,500, half were assessed as metabolically healthy after a physical examination and lab tests.

This subset of metabolically healthy obese people who did not suffer from conditions such as diabetes, high cholesterol or high blood pressure, were generally fitter and exercised more than the other obese people.

And their risk of developing or dying from cardiovascular disease or cancer was identical to people of ideal weight and was half that of "metabolically less fit" obese people.

Continue reading the main story
“
Start Quote

These studies remind us that it is not always your weight that's important, but where you carry fat and also how it affects your health and fitness”

Lead researcher Dr Francisco Ortega, who currently works at the University of Granada in Spain, said the findings show that getting more exercise can keep you healthier, even if you still carry a bit of extra weight.
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http://www.bbc.co.uk/news/health-19474239
 
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This is one of those times I'd love to see a poster of a crowd of a couple thousand people all lined up in rows according to their BMI. One photo might answer a lot of questions. :D
 
Actually, it's pure body size that matters... being taller doesn't make your heart any stronger than a short person's, and the extra artery length applies as much to tall people as it does to fat ones. Unfortunately, I had no say in the matter of being 6'4 (outside of malnutrition, anyway). However, it does have its perks in other ways. :D
 
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