BMI Survey

[sjs]

Just checking, but you are being sarcastic I take it?

IF no, then how exactly dose a weighing scales work out fat analysis?

I refer you to the link posted, you'll find all the information you need there.

If you mean the link in the post I'm quoting, there seems to be hardly any information. These scales work in the same way as all the others which claim to measure %age fat, namely by measuring impedance. This is known to be somewhat inaccurate, as some of the online reviews note.

None of the material linked to in this thread says anything much which isn't a) obvious and b) known for a long time. It just seems that the NHS may have decided to stop ignoring these objections. Having said that, my daughter had her BMI calculated only the other day, by a GP who was incapable of reading a number from a screen and quoting it to the two decimal places she deemed appropriate. BMI must be really important if it needs three significant figures.

[RogerThat]

According to the 'results' of this survey, 59% of the participants are either very overweight or obese. I wonder how that translates to the reality of active cyclists with large (gluteus) muscle mass. I don't doubt that some GPs use BMI and think it effective for a sedentary patient group, applying it to the physically active with large muscle mass is clearly ludicrous.

The danger with using BMI and not fat analysis as a measurement tool is that 35% of people with 'normal' BMI (under 25) have undiagnosed potentially life threatening illnesses and circulatory conditions which are missed by time strapped GPs who look at a chart, pop you on the the scales and declare you 'good to go'. How this translates into mortality rates is currently under investigation at York University. Around 30% of my own heart bypass/stent patients are 'normal' BMI and it is long term undiagnosed illness, smoking /drinking/ sedentary lifestyle which have necessitated surgical intervention, not a weight problem.

The medical establishment and statistical community have both highlighted the limitations of BMI. Because the BMI depends upon weight and the square of height, it ignores basic scaling laws whereby mass increases to the 3rd power of linear dimensions. Hence, larger individuals, even if they had exactly the same body shape and relative composition, always have a larger BMI. Also, its assumptions about the distribution between lean mass and adipose tissue are inexact. BMI generally overestimates adiposity on those with more lean body mass (e.g., athletes) and underestimates excess adiposity on those with less lean body mass. It's limitations also extend to children and the over 60's, in both cases it is widely ignored as a diagnostic tool for these groups. So what efficacious benefit has BMI in modern health care, virtually none that I can see, which is why the NHS is currently rolling it back in preference to a more technology driven diagnostic. That's the advice we currently give to the GPs of patients coming through our rehab.

BMI in GP surgeries is a meat cleaver tool when the delicacy of a scalpel is required. It's a formula designed in the 1830's and not practical at all in the 21st century. Being classified by 'BMI' as very overweight or obese can restrict your access to a wide variety of treatments. If your GP defines you this way (and you are physically active) I would certainly challenge the diagnoses and ask to be re-evaluated as a non sedentary person, preferably in a clinic which has specificity in this area.

[Graham]

I over-reacted to a ( complaint ) report earlier.

My apologies to anyone who mistook themselves for a target.

I have taken time to read through the topic more carefully.

[661-Pete]

Of course we don't expect a set of bathroom scales to be a sort of 'diagnose-everything' magic weapon - like the 'auto-doc' so cherished by many Sci-Fi writers! Indeed my father died of a heart attack when he was by no means overweight - I suspect that his BMI would have read 'normal' at the time. So his heart problems were evidently down to other root causes.

But surely we are not disputing the fact that being overweight - while not being the only cause of serious illness - is a significant factor. Surely those unfortunate and horribly obese people whom we all too often see waddling around the town or the supermarket aisle - if they're not confined to an invalid buggy that is - really do have a BIG problem! And monitoring your weight and adopting healthy eating habits is something we can all do at home - if we really try! There's no need to go to the doctor's surgery and take up their time, just to have your weight measured. It's DIY health monitoring - not a complete diagnostic, but a self-help tool that helps.

As for the bioelectrical impedance test - the only body fat measurement technique that most of us have the know-how to use in the home (not many of us have the space for a full-blown MRI scanner in the spare bedroom!) - well, I can look up in Wiki as well as the next person! It appears that the fat-measuring scales - as mentioned above - only measure impedance foot-to-foot, which is considered less reliable than 4-electrode or 8-electrode devices. Furthermore, it appears that the reading is strongly affected by recent meals, recent exercise, or dehydration of the body. So not all that easy to use! Maybe they work for some people, if used carefully.

I'll stick to the scales.

[Vorpal]

According to the 'results' of this survey, 59% of the participants are either very overweight or obese. I wonder how that translates to the reality of active cyclists with large (gluteus) muscle mass. I don't doubt that some GPs use BMI and think it effective for a sedentary patient group, applying it to the physically active with large muscle mass is clearly ludicrous.

I used have an annual medical at work. Every year they asked me, based upon my BMI, if I wanted advice about diet and exercise. I always had to ask the (rather plump) nurse if I looked like I needed it. I suggested on several occasions that if any of the medical staff could cycle with me the 28 miles from home to work, I might consider their advice.

[LollyKat]

That reminds me of a life-long cyclist friend who developed kidney failure in his 60s. While waiting for a transplant he took part in a sponsored climb of Ben Lomond to raise funds for a new scanner. He left his medical team behind gasping for breath, and wondering who was the one that was ill!

[531colin]

...........The danger with using BMI and not fat analysis as a measurement tool is that 35% of people with 'normal' BMI (under 25) have undiagnosed potentially life threatening illnesses and circulatory conditions which are missed by time strapped GPs who look at a chart, pop you on the the scales and declare you 'good to go'. How this translates into mortality rates is currently under investigation at York University. Around 30% of my own heart bypass/stent patients are 'normal' BMI and it is long term undiagnosed illness, smoking /drinking/ sedentary lifestyle which have necessitated surgical intervention, not a weight problem. .......

If 30% of your cardiac patients have "normal" BMI, that leaves a mere 70% of your cardiac patients with an "abnormal" BMI?
If that 30% of cases are due to long term illness/smoking/drinking/sedentary lifestyle, would fat analysis have identified these patients anyway?

35% of people with normal BMI have an undiagnosed life threatening illness/circulatory condition. 35% of what population? People who go to their GP with breathlessness or chest pain? 35% of people over 60 years old? What conditions? High blood pressure/cholesterol? And the same question....would fat analysis find these patients? Because if it won't, you are just wanting to swap one flawed test for another, and the GP will still be strapped for time and wanting the patient out of the door ASAP.

[RogerThat]

One in three people who present at GP surgeries (35%) with normal bmi will develop a serious illness which has probably been missed by a combination of error, lack of time and the wrong assumption that because they present with bmi <25 then a whole host of what I would consider mandatory checks go unperformed . We've been trying to educate GPs on this for five years now, such is the ludicrous entrenchment of BMI as a 'scientific' methodology. I can show you data that concludes one in every two GPs who's fundamental understanding of obesity is either wrong or 20 years out of date. Does that sound reassuring to you?

At the other end of the scale, those presenting with higher BMI (including likely the vast majority of active cyclists and other athletes with large % of well developed gluteus musculature) are wrongly diagnosed as very overweight or obese. As I've said previously this prevents them access to a large number of treatments.

BMI is also pretty useless on the young and essentially useless for the over 60's.

It's an outdated and vastly superceded methodology. I and a colleague from Oxford university have been lobbying the Nhs at the highest level for eighteen months to have it removed wholesale from the website and and literature, such is the seriousness we take it, as a poor medical tool. York University medical school are currently evaluating the mortality rate of GP surgeries who use BMI in preference to % body fat. I've seen the initial results of the study. I've been practicing in the NHS for 35 years, I've seen a lot of data relating to bad practice over the years, and it has frightened me.

[531colin]

Yes, I did "bother to read it".
BMI is flawed....I get it.
You want to substitute a different test, I get that, too.
Fairly straightforward question, a one word answer will do.....
...........will your new test pick up the one in three patients who are currently missed because they have a normal BMI?

[Edwards]

I am not sure if I have this correct.

I am no longer supposed to use scales, height, and general looking for fat or muscle to get a rough idea if I am overweight.

I am supposed to go out a spend £90 on some thing that is not that accurate depending on if I have sweaty feet, not enough liquid/to much liquid for lunch and a whole bunch of other stuff.

I only want to know what approximate weight range is best for my height and fitness. So if others who take some exercise are the same height and weight as me then I should be about average?

Is this not simplified to BMI for an active person?
If so then the variable is the amount and type of activity.

[RogerThat]

Yes, I did "bother to read it".
BMI is flawed....I get it.
You want to substitute a different test, I get that, too.
Fairly straightforward question, a one word answer will do.....
...........will your new test pick up the one in three patients who are currently missed because they have a normal BMI?

Yes.

[RogerThat]

I am not sure if I have this correct.

I am no longer supposed to use scales, height, and general looking for fat or muscle to get a rough idea if I am overweight.

I am supposed to go out a spend £90 on some thing that is not that accurate depending on if I have sweaty feet, not enough liquid/to much liquid for lunch and a whole bunch of other stuff.

I only want to know what approximate weight range is best for my height and fitness. So if others who take some exercise are the same height and weight as me then I should be about average?

Is this not simplified to BMI for an active person?
If so then the variable is the amount and type of activity.

Go to your doctor or better still a wellness clinic who specialises in obesity and ask for a % body fat evaluation. They will use several methods to determine it, giving you a definitive answer to your question. You need not spend a penny. Anyone who tells you BMI is an accurate measure for an active cyclist is simply giving you erroneous and dated information which may eventually restrict your access to essential treatments on the NHS.

[axel_knutt]

Go to your doctor or better still a wellness clinic who specialises in obesity and ask for a % body fat evaluation.

More worried well to clog up the system.

I think the difference between muscle and fat is lost on some doctors, a year after I had given up training I told a doctor that my ribcage had disappeared under a thick layer of fat, but my weight was the same. She just looked at me as if I had told her that I'd been for a joy ride in a Martians flying saucer.

[RogerThat]

Go to your doctor or better still a wellness clinic who specialises in obesity and ask for a % body fat evaluation.

More worried well to clog up the system.

I think the difference between muscle and fat is lost on some doctors, a year after I had given up training I told a doctor that my ribcage had disappeared under a thick layer of fat, but my weight was the same. She just looked at me as if I had told her that I'd been for a joy ride in a Martians flying saucer.

GPs are notorious for not taking into consideration the physical (and mental) advantage that the 'active well ' have over the majority sedentary population.

[Edwards]

GPs are notorious for not taking into consideration the physical (and mental) advantage that the 'active well ' have over the majority sedentary population.

Yet you told me to go to the doctors.

You advised purchasing some gadget.

I do know a visit to the doctors is still free for now.

All that was asked for was a general idea of weight to height of non sedentary people who also cycle. Yet you keep on with the accuracy thing.