Combining body mass index with other measurements and tests would lead to better care and outcomes, experts say

An alternative to BMI for diagnosing obesity could prevent misdiagnosis in millions of people worldwide, according to doctors who found it more accurately distinguished healthy people from those with harmful excess body fat.

Medical experts have long considered body mass index a blunt instrument for defining obesity, leading to concerns that substantial numbers of people with excess body fat are missed while others who are healthy are wrongly diagnosed.

The new approach, which combines BMI with other body measurements and organ function tests, suggests BMI alone misses obesity in 5-9% of adults, while wrongly diagnosing the condition in as many as 3%.

“This misclassification can account for tens of millions of people, so the inaccuracy of BMI is a big problem at scale and also for individuals,” said Francisco Rubino, a professor of metabolic and bariatric surgery at King’s College London.

  • hakase@lemmy.zip
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    3 days ago

    Any improvement in diagnosis is certainly to be celebrated, but I was surprised to find out that BMI only wrongly diagnosed obesity less than 3% of the time.

    Seems like it’s already much more accurate than it usually gets credit for.

    • exasperation@lemmy.dbzer0.com
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      3 days ago

      Yeah, that’s a lot more accurate than conventional wisdom seems to suggest.

      If BMI says you’re obese, you only have a 3% chance of not actually being obese? That’s a pretty accurate diagnostic.

      • JustEnoughDucks@feddit.nl
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        3 days ago

        Yeah it is accurate for the overwhelming majority, sedentary population.

        When you get to people who actively work out hard, regulary, (much of that 3% I would guess), then it is wildly inaccurate.

    • thanksforallthefish@literature.cafe
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      3 days ago

      I could be wrong but your wording suggests you’re misreading that.

      Article states false positive rate is 3% and false negative is 5-9%

      That’s obviously not the same as wrong 3% of the time.

      If we assume even tails then 8-12% of the time BMI incorrectly diagnoses.

      Which is about what I’d expect. BMI is an approximate fit model, the further you get from the mean the less useful it is. If you are more than 1 standard deviation from the height mean you are much more likely to get a false positive (if you’re short) or false negative (if you’re tall).

      In other words it’s a line of best fit that doesn’t work for outliers

      • hakase@lemmy.zip
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        3 days ago

        I was specifically referring to the enormous number of people who claim that they’ve only been diagnosed as obese due to the inaccuracy of BMI as a measure, not the (even larger) number of people who should be diagnosed as obese but aren’t.

        • zero924@lemmy.blahaj.zone
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          2 days ago

          I’ve literally never seen a single person actually claim that about themselves. I’ve seen plenty of people point out the flaw of just using weight and height to diagnose others as overweight or obese, which is supported by literally all of the evidence in front of you. But I’ve never seen a conversation where someone’s BMI somehow came up and they claimed that actually they’re perfectly fit and it’s a problem with BMI as a measurement. That’s just not a thing that happens outside of the fantasies of fatphobic weirdos

    • LincolnsDogFido@lemmy.zip
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      3 days ago

      I think you’re probably conflating obese and ‘overweight’ in regards to seemingly fit or athletic body types. BMI is still notoriously inaccurate when trying to define regulars at a gym or athletes. It often lables them as overweight due to muscle mass being more dense than body fat. But it’s pretty difficult to have that body type and lifestyle but be labeled as obese. For example, at my height I would need to weigh 220lbs to be obese. It’s doable considering the 3% figure but unlikly.

  • velma@sh.itjust.works
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    3 days ago

    Good news! BMI has always been a limited way of measuring obesity. It’s nice to see this advancement.

  • OfCourseNot@fedia.io
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    3 days ago

    So there are even more obese people than we previously thought then? If, yesterday, you were overweight with a belly you are now obese.

    • CanIFishHere@lemmy.ca
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      3 days ago

      The way to read that is: “there are more people with obese related health risks than previously thought.” That’s the takeaway.

  • vagrancyand@sh.itjust.works
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    3 days ago

    You mean the thing testing people to the standards of 19th century peasants might be just a little outdated and inaccurate?