Do BMI's seem unrealistic to anyone else?

Of course, BMI looks at populations, not individuals. Understood, no explanation needed.

But if a person's BMI is 50, yes, a second look is in order, imo. Measure a wrist. A waist. Take the pinch test. IT's a SCREENING tool that SHOULD lead to more screening.

I never once said BMI was uncomplicated. Only that they indicate obesity often enough to be reviewed. Because of AVERAGES.

Bodyfat percentage estimates as a better indicator? Oh sure, lets get every GP to send every patient for hydrostatic weighing, or annual DEXA scans. No? Oh wait let's teach them to use the callipers correctly. No? Oh there are those scales. :noway:

All these measures are estimates and guides only, none is perfect. It would be great if some calculation came out that was more inclusive and easier to use. But I urge people to use common sense. Use more than one method.

***

Can you address the comparative rates of obesity across countries, please, and how that removes individual variation from the equation, and what that then means?

Ethnic mix, well, there aren't THAT many differences in height, across most countries. If any exist, they're not often hugely significant.

Ethnic mix, well, there aren't THAT many differences in height, across most countries. If any exist, they're not often hugely significant.

You've obviously never walked through a native market in Guatemala.

yeah this is patently false. you're saying from the phillipines to the nordic countries, there isn't much difference in height? reeeeally?

Of course, BMI looks at populations, not individuals. Understood, no explanation needed.

well the problem is that the vast majority of people, including many health professionals don't take them that way. It is used by many as a diagnostic tool. it's used in the military as a diagnostic tool

But if a person's BMI is 50, yes, a second look is in order, imo. Measure a wrist. A waist. Take the pinch test. IT's a SCREENING tool that SHOULD lead to more screening.

wrist measurements are not reliable, plus if someone has that much body fat, the fat around their wrists will skew the result.

If someone's BMI is that high, it doesn't take a chart to see that they're obese. People who are that obese look obese, the doctor can simply refer them for other measures, without needing a BMI chart. Studies in the UK have shown that waist circumference is a better predictor of health risk than BMI, and so for people who don't look particularly fat, but for whom the doctor wants to be sure about, well the doctor can measure their waist.

People who are "overweight" according to BMI but are not over fat, do not look fat. They may look athletic or heavily built, but then doctors still come in with the BMI chart and based solely on numbers without even looking at the person, or even when they can see that they are athletic build, will tell them that BMI says they're overweight. I've heard soooo many cases of this, it's not like they're one offs. There are a number of health professionals who believe that it doesn't matter how thin or muscular someone looks, it's being heavy that puts their health at risk. and even more of Joe Public who think this.

I never once said BMI was uncomplicated. Only that they indicate obesity often enough to be reviewed. Because of AVERAGES.

Bodyfat percentage estimates as a better indicator? Oh sure, lets get every GP to send every patient for hydrostatic weighing, or annual DEXA scans. No? Oh wait let's teach them to use the callipers correctly. No? Oh there are those scales. :noway:

yes, that's what they should do. Callipers, circumference measures plus some common sense. I mean 7 years in medical school and no-one can teach them to use callipers to screen for obesity? Come on! Additionally, you can look at an athletic person and see they're not fat. go check out Leigh Peele's blog for how to measure body fat percentage and visual estimates.

Like I said, I've read studies that show that a simple waist measurement is a better predictor of health risk related to obesity than BMI, and in the UK, there has been some effort to get this to phase out BMI charts. there's also waist to hip ratio, and circumference body fat percentage methods such as the Navy formula. Additionally, callipers are not beyond the expertise of people who have gone to university. I learned to use them for my undergraduate study at university. they're not *that* difficult, and if a doctor thinks that the results are not accurate, then they can look at other measurements too. And how much training does it take someone to be able to use a tape measure correctly?

Actually some insurance companies will send people with high BMIs to DEXA scans to determine if they're actually overfat or if they're athletic and large framed, and the results of the test determine how expensive their policy is, i.e. heavy and athletic = discount, heavy and overfat = higher rate due to the higher risk from the obesity

All these measures are estimates and guides only, none is perfect. It would be great if some calculation came out that was more inclusive and easier to use. But I urge people to use common sense. Use more than one method.

Yes absolutely, they're estimates, and many of them are better estimates than BMI. I agree use more than one method, but BMI really doesn't need to be in there, and there absolutely is a need for it to not be used as a diagnostic tool any more. You're saying it should be used as a screening tool.... well a) there are better screening tools and b) lots of people including lots of health professionals don't use it as a screening tool, they use it as a diagnostic tool, and without the common sense to realise that it doesn't apply to everyone.

Ethnic mix, well, there aren't THAT many differences in height, across most countries. If any exist, they're not often hugely significant.

I'm not talking about just height, I'm talking about height and frame size. Fact is that human variation tends to go from short and large framed (cold adapted), to tall and slender framed (tropical/dry adapted). People with cold adapted body proportions, like me, have a significantly higher BMI than people with tropical body proportions. That comes from evolution and you do see trends in modern human populations in this direction, which is why Northern European countries tend to have a higher healthy BMI range than people in Southern Asian countries.

In the UK I've read several articles about the need to adjust the BMI range for British Pakistanis, so they are diagnosed with being overweight and obese at lower BMIs than the indigenous British population, and it's because of this. Also, Japan has a lower healthy BMI range than Europe too, because Japanese people tend to be smaller framed than Europeans. There are more factors at play than simply climate in terms of why these differences exist (i.e. there are a lot more body types than cold adapted and tropical), but there are definitely enough ethnic differences for doctors and researchers to be proposing different healthy ranges for different people.

This can be misleading though, because you will get people in every population that don't follow the trend, i.e. tall, small framed people from cold places, and short, large framed people from tropical places, and within group variation in all poulations. I'm significantly below average height for my ethnic group, and above average in my frame size for probably any modern population.

The thing is, when you have to make so many adjustments... frame size, ethnicity, degree of athleticisim... you may aswell just abandon BMI altogether for something that is simply a better screening tool, which is why in the UK there's been a lot of moves towards using waist circumference instead of BMI for screening, because there's not much in someone's waist that can make it that much bigger, other than fat, plus visceral fat (fat around the abdominal organs) is more closely tied to health risk than subcutaneous fat - and if there's another health problem e.g. abdominal bloating causing the increased waist measurement, well that's something the doctor needs to know about - the abs muscle does not bulk up like other muscles do, so muscle mass is less likely to confound results.... but doctors are slow to actually make the changes, even though the NHS is actually recommending this.

But you should reject that anyway, because as neandermagnon has been saying about bmi, variation within groups is greater than variation without. So why bother?

If you're saying why bother adjust BMI, then yes I'd agree. Just chuck BMI in the bin.

There are significant differences in average populations BMI that result from natural selection for particular climates/environments though. (and probably some differences in some populations due to genetic drift too)

I don't know why you're so heavily defending BMI. There are better ways to screen for obesity and by the time you've adjusted it to account for individual differences, you may as well have just measured something else to begin with.

I'd say use waist circumference as a basic screening tool, and body fat percentage as a diagnostic tool, and yes, train doctors and nurses in how to use callipers.

Of course, BMI looks at populations, not individuals. Understood, no explanation needed.

well the problem is that the vast majority of people, including many health professionals don't take them that way. It is used by many as a diagnostic tool. it's used in the military as a diagnostic tool

But if a person's BMI is 50, yes, a second look is in order, imo. Measure a wrist. A waist. Take the pinch test. IT's a SCREENING tool that SHOULD lead to more screening.

wrist measurements are not reliable, plus if someone has that much body fat, the fat around their wrists will skew the result.

If someone's BMI is that high, it doesn't take a chart to see that they're obese. People who are that obese look obese, the doctor can simply refer them for other measures, without needing a BMI chart. Studies in the UK have shown that waist circumference is a better predictor of health risk than BMI, and so for people who don't look particularly fat, but for whom the doctor wants to be sure about, well the doctor can measure their waist.

People who are "overweight" according to BMI but are not over fat, do not look fat. They may look athletic or heavily built, but then doctors still come in with the BMI chart and based solely on numbers without even looking at the person, or even when they can see that they are athletic build, will tell them that BMI says they're overweight. I've heard soooo many cases of this, it's not like they're one offs. There are a number of health professionals who believe that it doesn't matter how thin or muscular someone looks, it's being heavy that puts their health at risk. and even more of Joe Public who think this.

I never once said BMI was uncomplicated. Only that they indicate obesity often enough to be reviewed. Because of AVERAGES.

Bodyfat percentage estimates as a better indicator? Oh sure, lets get every GP to send every patient for hydrostatic weighing, or annual DEXA scans. No? Oh wait let's teach them to use the callipers correctly. No? Oh there are those scales. :noway:

yes, that's what they should do. Callipers, circumference measures plus some common sense. I mean 7 years in medical school and no-one can teach them to use callipers to screen for obesity? Come on! Additionally, you can look at an athletic person and see they're not fat. go check out Leigh Peele's blog for how to measure body fat percentage and visual estimates.

Like I said, I've read studies that show that a simple waist measurement is a better predictor of health risk related to obesity than BMI, and in the UK, there has been some effort to get this to phase out BMI charts. there's also waist to hip ratio, and circumference body fat percentage methods such as the Navy formula. Additionally, callipers are not beyond the expertise of people who have gone to university. I learned to use them for my undergraduate study at university. they're not *that* difficult, and if a doctor thinks that the results are not accurate, then they can look at other measurements too. And how much training does it take someone to be able to use a tape measure correctly?

Actually some insurance companies will send people with high BMIs to DEXA scans to determine if they're actually overfat or if they're athletic and large framed, and the results of the test determine how expensive their policy is, i.e. heavy and athletic = discount, heavy and overfat = higher rate due to the higher risk from the obesity

All these measures are estimates and guides only, none is perfect. It would be great if some calculation came out that was more inclusive and easier to use. But I urge people to use common sense. Use more than one method.

Yes absolutely, they're estimates, and many of them are better estimates than BMI. I agree use more than one method, but BMI really doesn't need to be in there, and there absolutely is a need for it to not be used as a diagnostic tool any more. You're saying it should be used as a screening tool.... well a) there are better screening tools and b) lots of people including lots of health professionals don't use it as a screening tool, they use it as a diagnostic tool, and without the common sense to realise that it doesn't apply to everyone.

Ethnic mix, well, there aren't THAT many differences in height, across most countries. If any exist, they're not often hugely significant.

I'm not talking about just height, I'm talking about height and frame size. Fact is that human variation tends to go from short and large framed (cold adapted), to tall and slender framed (tropical/dry adapted). People with cold adapted body proportions, like me, have a significantly higher BMI than people with tropical body proportions. That comes from evolution and you do see trends in modern human populations in this direction, which is why Northern European countries tend to have a higher healthy BMI range than people in Southern Asian countries.

In the UK I've read several articles about the need to adjust the BMI range for British Pakistanis, so they are diagnosed with being overweight and obese at lower BMIs than the indigenous British population, and it's because of this. Also, Japan has a lower healthy BMI range than Europe too, because Japanese people tend to be smaller framed than Europeans. There are more factors at play than simply climate in terms of why these differences exist (i.e. there are a lot more body types than cold adapted and tropical), but there are definitely enough ethnic differences for doctors and researchers to be proposing different healthy ranges for different people.

This can be misleading though, because you will get people in every population that don't follow the trend, i.e. tall, small framed people from cold places, and short, large framed people from tropical places, and within group variation in all poulations. I'm significantly below average height for my ethnic group, and above average in my frame size for probably any modern population.

The thing is, when you have to make so many adjustments... frame size, ethnicity, degree of athleticisim... you may aswell just abandon BMI altogether for something that is simply a better screening tool, which is why in the UK there's been a lot of moves towards using waist circumference instead of BMI for screening, because there's not much in someone's waist that can make it that much bigger, other than fat, plus visceral fat (fat around the abdominal organs) is more closely tied to health risk than subcutaneous fat - and if there's another health problem e.g. abdominal bloating causing the increased waist measurement, well that's something the doctor needs to know about - the abs muscle does not bulk up like other muscles do, so muscle mass is less likely to confound results.... but doctors are slow to actually make the changes, even though the NHS is actually recommending this.

I'm all for a more accurate tool, and for sensible application of the ones currently available, in clinical practice. Waist circumferences is better, I agree, and there's the new BMI, and the BAI.

I am not hopeful that doctors would be willing to submit to training to take reliable caliper measurements. Even personal trainers and fitness specialists, who do that kind of thing all day, can't often get it right. Anything that requires expertise is always going to be tougher to use in practice than some kind of algorithm.

In my dreams, practices/surgeries would invest in eg nurses specially trained in public health/obesity to use all relevant measures.

I'm not especially enamoured with the BMI, it's just a familiar starting point. Flawed as it is, though, and taking it with a grain of salt, it's hard to ignore the big differences it shows between the US and other regions with grossly similar population distributions. (Take e.g. Canada as one point of comparison, and then Europe as a whole). I don't think it's crazy to suggest that most Americans are probably overfat in ways that incline them to ill health. Most Americans with BMIs of 30+ are probably not exceptions.

Well, that's a funny chart. The WHO doesn't even have data for half the countries on there, for 2008 (which your chart's meant to represent):

http://apps.who.int/bmi/index.jsp < WHO just had data for a few countries in 2008

http://apps.who.int/bmi/index.jsp < most recent worldwide

Bottom line: are most Americans probably overfat? Do most of them lie to themselves about it? (Yes, we are really good at lying to ourselves or misperceiving things, especially when whole industries help it along [like clothing manufacturers with their vanity sizing]).

If the BMI is as widely disregarded as it is, maybe whr should be used instead. But there will be criticisms of that too.

I'm not saying any old thing should be used. Until now the BMI's been used. Badly, often, true. But it's a starting point, an initial screening tool, that I think is still worth attending to in the absence of wholesale takeup of other methods. And, yes, it ought to be followed up with a more comprehensive evaluation in a clinical setting.

It's like with environmental toxins. Is any level of exposure safe for a given toxin x (obviously particulars matter here, lol)?

Research obviously informs the decision, but 'safe levels' ultimately are set through political, pragmatic decision-making processes, which weigh a range of costs and benefits. You need something that can be used pragmatically, that works well enough to make initial determinations.

All those risks we discussed *are* higher, just using the BMI. Good enough for me (until most practioners accept the use of whichever metric's better). Look here:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1890993/

he objectives of this study were to explore the relation between body mass index (BMI) and prevalence of diabetes mellitus, hypertension and dyslipidaemia; examine BMI distributions among patients with these conditions; and compare results from two national surveys.
...

Increased BMI was associated with increased prevalence of diabetes mellitus, hypertension and dyslipidaemia in both studies (p < 0.001). For each condition, more than 75% of patients had BMI ≥ 25 kg/m2.

Is that really meaningless, though bf% wasn't used?

Here's a great question:

How many of you here that state you cannot achieve a healthy BMI are olympic athletes?


Yeah. That's what I thought.

Your post is non-sensical. I'm not an olympic athlete and would be extremely unhealthy with a"normal" BMI. When you can see my abs quite well from a distance I'm at about 27.0 on BMI. When I cut enough to be seriously ripped I'm at a BMI of 26.2 ...

If you'd bother to read the posts, you'd realize BMI is accurate only for those close to 'average' in terms of height, lean-mass, bone-density and those that are neither mesomorphs or ectomorphs.

If you've reached a "healthy" BMI for you - congratulations, you've reached what for many is a completely meaningless statistic.

chiming in on this one because i've also struggled to reach a healthy BMI as part of my weight loss. currently in maintenance mode - although i'd be stoked if i could lose another 5 lbs or so. my BMI is still at the higher end of 24 and i'm only 2 lbs away from the overweight category. i also used to believe a healthy BMI would be ridiculously too slim for me but that's not the case. although i'm happy with my current weight, like most women here who struggle with that little tummy pouch, i'd like mine to get smaller too. i'm only 5'1" and currently 125 lbs. my goal is 120 despite BMI charts stating i should be 100 - 110 lbs as an ideal weight. that might look marvelous on a teenager but i'm nearly 40. that weight would have me looking skeletal and sick.