Proof that ‘body mass index’ is useless: a quarter of those classed as obese are actually healthy

A study led by psychologists at the University of California, Los Angeles, has found that the body mass index (BMI) scale incorrectly labels people as ‘unhealthy’. The findings have been published online in the International Journal of Obesity.

The researchers examined the link between BMI — which is calculated by dividing a person’s weight by their height — and several health markers, including blood pressure and glucose, cholesterol and triglyceride levels.

They found that close to half of those considered overweight are actually healthy, as are more than a quarter of people considered clinically obese.

Janet Tomiyama, the study’s lead author, said: ‘Many people see obesity as a death sentence. But the data shows there are tens of millions of people who are overweight and obese and are perfectly healthy.

‘There are healthy people who could be penalised based on a faulty health measure, while the unhealthy people of normal weight will fly under the radar and won’t get charged more for their health insurance. Employers, policy makers and insurance companies should focus on actual health markers.’

The researchers also discovered that over 30 per cent of those with BMIs in the ‘normal’ range are actually unhealthy based on their other health data.

Jeffrey Hunger, a co-author of the paper, said the research shows that BMI is a deeply flawed measure of health. ‘This should be the final nail in the coffin for BMI,’ he said.


  • Summer Isles

    The psychologist who led on this paper is slightly missing the point.

    Raised BMI is not an illness any more than smoking is an illness. It is a risk factor for illness, especially diabetes.

    There is ample evidence for this, for example :

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

    • Mr B J Mann

      No, it isn’t.

      Even the guy who developed the index said you couldn’t use it to determine anything about individuals, it was purely a (rough) measure of the general health of a population. And it’s very rough: the proper rough equation has cube roots and things, which weren’t easy to do in pre calculator days, so he simplified it to what is used now. Also he was aware that healthy BMI changed with age, the index should only be used for average young adults.

      But the big problem is that the bands are completely artificial, and then were arbitrary lowered.

      If I said that I’ve measured the likelihood of death from falling from different heights and you were a thousand times more likely to die from falling more than a foot than falling less than a foot would you argue you were highly likely to die if you fell 13 inches?!

      Research has shown that, actually, the healthiest people are those classed as slightly “obese”. But they have been lumped in with the morbidly obese and then “experts” point at the category which contains really, really unhealthily overweight and shout, oh, look, if you are in that category you are x times more likely to die.

      But just like lumping 13 inch falls with 100 foot falls doesn’t make 13 inch falls dangerous, lumping people with healthy BMIs in with grossly unhealthy ones doesn’t make healthy BMIs unhealthy!

      • Summer Isles

        Again you are missing my point, if you follow the link it takes you to one of the many papers that confirm that being overweight increases the risk of diabetes and other metabolic diseases.

        For that reason it is sensible to avoid being overweight, in the same way as it is sensible to avoid smoking.

        In the traditional Spectator Health manner this basic clinical point is transmuted into an indignant debate about whether or not medical advice amounts to a row of beans which is fair enough but it doesn’t alter the facts.

        • Mr B J Mann

          Again, YOU are missing MY point.

          The fact that that being in an over 1 foot fall increases the risk of death and other metabolic disruption doesn’t mean that falling 13 inches kills.

          For that reason it is sensible to avoid being dangerously overweight, in the same way as it is sensible to avoid falling a dangerous distance.

          But it doesn’t mean falling more than an arbitrary figure is dangerous.

          The “Overweight” and “Obese” bands are arbitrary, they don’t reflect what should be good health advice.

          Hence the “indignant” debate!

          It’s about whether the arbitrary bands and altered “facts” amount to a row of beans, not whether advice not to be DANGEROUSLY overweight should be ignored.

          • Summer Isles

            Please don’t shout, it’s rude.

            You are free to believe whatever you like about what is and is not good health advice.

            GPs have around sixty patient contacts a day, some of them come into the consulting room like your good self seething with indignation before a word has been spoken.

            The practical issue, which needs to be dealt with alongside a host of other issues within ten minutes, is how to identify those patients who are a greater risk of diabetes.

            The research that I have linked to suggests that BMI is a useful indicator.

            That is the way it is.

          • Mr B J Mann

            Please don’t be rude, it’s rude.

            You have no idea whether I was vocalising while typing, never mind at what volume, and even if you did it would be the height of bad manners to comment on it, never mind publicise it.

            It’s ruder still to accuse someone who you don’t even know, never mind have never seen in a surgery, of coming into the consulting room not just seething with indignation, but seething with indignation before a word has been spoken!

            If you’d had the courtesy to ask, you would have found that, apart from anything I’ve gleaned from publicly available information on the matter, I have been told on more than one occasion by my GPs and Consultants that such artificial limits as the “safe” BMI, and cholesterol, limits are a nonsense. I’ve also been told by a nurse who was checking my BMI that an over the “safe” BMI level wasn’t necessarily a problem.

            And I’ve already pointed out some of the problems with BMI values.

            Feel free to point me in the direction of SCIENTIFIC PROOF (emphasised as a courtesy for the hard of reading) that the healthiest BMI is in the low 20s, as opposed to opinion that is nothing more than current dogma.

            Before you do, you might want to read this guide for laymen on BMI “research”:

            http://www.independent.co.uk/life-style/health-and-families/features/why-being-overweight-means-you-live-longer-the-way-scientists-twist-the-facts-10158229.html

          • Summer Isles

            Using block capitals in internet communication is generally accepted as shouting, please don’t do it.

            The links below are to the US National Library of Medicine and confirms the link between BMI and diabetes risk. As a retired GP I rely more on that kind of source than on newspapers.

            I should be simply astonished if any of my former colleagues had told you that being overweight is a not health risk.

            BMI is not a perfect measure but in extremely busy day to day clinical practice it is the best available. It is certainly preferable to looking someone up and down and telling them they are fat which would, quite understandably, cause offence.

            If you can’t or won’t accept what I am saying there is nothing more to say.

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

            http://care.diabetesjournals.org/content/30/6/1562.short

          • Mr B J Mann

            Sory, but when were you promoted to chief constable, or, rather, Chief Constable (see what i, or, rather I, did there, or SWIDT for short).

            And I think you’ll find it’s BLOCKS of capitals.

            When handwriting, “printng” in ALL block capitals can be more legible than

          • Avishek Saha

            Why are you freaking out? I don’t see the need for so much energy expenditure on internet comments.

            All I have to say in response to you is that it’s still not fair to say that being slightly obese is the healthiest weight to be at. That is an absurdly unscientific overgeneralized statement. For what age group are you talking about? It’s impossible for me to get to a BMI of 30+ right now. my body maintains it’s weight and I can’t forcibly gain weight.

            I agree with you and this article as the research has showed this for decades. Anyone who thinks obesity is automatically bad has no idea what they’re talking about. But we must avoid over-generalization and be as specific as possible in defining the patient population.

          • Kristel Van Esbroeck

            I have been battling obesity since I was young (I was put on a diet at age 6 by my GP, who found no change in my weight during and after the program). For years I have been going to the gym, ate well, followed anything my nutritionist or GP said, even took prescribed fat blockers. Nothing helped. In fact, after about a month, I gained weight with every different program I followed.

            Recently I have also found out that I have progesterone sensitivity. Which causes weight gain. But trying to explain to someone that, yes I am morbidly obese, but NO, I do not eat like a pig and sit on my behind all day, is impossible. Or even explaining that my blood values are ridiculously healthy (bp of 60/90 average and heart rate of 60-65 at rest with good Cholesterol levels) despite my weight, is often received as a lie although the GP has that info on their files.

            I am in the middle of trying to get sterilized as a result of being unable to take any form of contraception due to the progesterone issue. Guess what, my BMI is stopping it. I have to once again go on a diet (wasting half a year again) to prove that I am healthy, rather than someone checking my levels of cholesterol, bp, heart rate and glucose levels.

            A lot of obese people are being judged as unhealthy, despite being more healthy than “normal” people. BMI calculations are no longer correct when speaking medically.

          • Mr B J Mann

            The links below are to the US National Library of Medicine and confirm the link between BMI and diabetes risk. As a retired GP I rely more on that kind of source than on newspapers.

            If you had bothered to read my link you would have found the reason I had described it as a:

            guide for laymen on BMI “research”

            And also perhaps why it would be even more useful for retired GPS with (too much?) time on their hands:

            Dr Malcolm Kendrick is a GP and researcher. This article is based on extracts from his book, ‘Doctoring Data: How to Sort Out Medical Advice from Medical Nonsense’ (Columbus, £14.99)

            You might want to check if the “research” you link to is already adressed by him.

          • Mr B J Mann

            I should be simply astonished if any of my former colleagues had told you that being overweight is not a health risk.

            No doubt.

            But here’s what the practising GP, sorry, gp, and researcher, concluded his “newspaper” article with:

            So, while I cannot tell you when “obesity” becomes a major health problem, I can definitely tell you that being “overweight” is the healthiest and most “normal” weight of all.

  • Tom Sykes

    It is an indicator, that’s all.
    Every 1st class rugby player “fails”