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> BMI characterized 26% of the subjects as obese, while DXA indicated that 64% of them were obese. 39% of the subjects were classified as non-obese by BMI, but

> BMI characterized 26% of the subjects as obese, while DXA indicated that 64% of them were obese. 39% of the subjects were classified as non-obese by BMI, but were found to be obese by DXA. BMI misclassified 25% men and 48% women. Just goes to show how unreliable BMI is… oh wait

deleted 4y ago
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pancrufty 4y ago
“Happily obese” people like to point out how wrong BMI is. Little did they know they were right for the wrong reason.
- makeitdouble 4y ago
  Is there anybody (obese and non obese) in the health community that assumes BMI isn‘t wrong ? I’m not sure what your point is.
  - swatcoder 4y ago
    I’m surprised this needs to be explained, but the joke is that every time BMI comes up in online discussions, people rally to annonuce that it’s too conservative because it classifies some dedicated bodybuilders as obese, while this study shows that it’s aggregate bias seems to be in precisely the opposite direction. Which, of course, better fits everyday intuition about how unhealthy most people with high BMI seem to be. In reality, the failure of BMI to accurately capture the body fat and healthfulness of most individuals is not usually because they’re just too damned ripped. It’s because people eat more and sit more than they ever have.
    - NavinF 4y ago
      Yep just below this thread there's a [dead] comment about how a bodybuilder had high BMI despite not being fat. It's always the same cliche.
      - d0mine 4y ago
        Pointing out that Earth is round no matter how often it is repeated does not become any less true. BMI and bodybuilder example may be less obvious unless you know that muscles are more dense than fat but it is true nonetheless.
    - makeitdouble 4y ago
      > people rally to annonuce that it’s too conservative That’s a bit of a surprise to me. The most common conplaint I heard was “it’s wrong, but we need to keep it around otherwise there’s no way to compare cross-studies”. We have decades and decades of BMI based classification, and publishing a paper today that needs results from past studies will automatically bind it to BMI. Same on public policies, defining obesity threshold a completely different way would require more politics than most groups are able to tackle. It’s like coming up today with a different way to count nutrients from calories, technical merit won’t make it prevail over the whole world that has been built around calories.
johntb86 4y ago
The paper mentions that "In 1995, the World Health Organization (WHO) defined obesity based on a percent body fat ≥25% for men and ≥35% for women [15], while the most recent 2009 guideline [..] used percent body fat ≥25% for men and ≥30% for women". I wonder what the process was for choosing the BMI and obesity cut-points, since they seem to differ a lot.

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pancrufty 4y ago

“Happily obese” people like to point out how wrong BMI is. Little did they know they were right for the wrong reason.

makeitdouble 4y ago
Is there anybody (obese and non obese) in the health community that assumes BMI isn‘t wrong ? I’m not sure what your point is.
- swatcoder 4y ago
  I’m surprised this needs to be explained, but the joke is that every time BMI comes up in online discussions, people rally to annonuce that it’s too conservative because it classifies some dedicated bodybuilders as obese, while this study shows that it’s aggregate bias seems to be in precisely the opposite direction. Which, of course, better fits everyday intuition about how unhealthy most people with high BMI seem to be. In reality, the failure of BMI to accurately capture the body fat and healthfulness of most individuals is not usually because they’re just too damned ripped. It’s because people eat more and sit more than they ever have.
  - NavinF 4y ago
    Yep just below this thread there's a [dead] comment about how a bodybuilder had high BMI despite not being fat. It's always the same cliche.
    - d0mine 4y ago
      Pointing out that Earth is round no matter how often it is repeated does not become any less true. BMI and bodybuilder example may be less obvious unless you know that muscles are more dense than fat but it is true nonetheless.
  - makeitdouble 4y ago
    > people rally to annonuce that it’s too conservative That’s a bit of a surprise to me. The most common conplaint I heard was “it’s wrong, but we need to keep it around otherwise there’s no way to compare cross-studies”. We have decades and decades of BMI based classification, and publishing a paper today that needs results from past studies will automatically bind it to BMI. Same on public policies, defining obesity threshold a completely different way would require more politics than most groups are able to tackle. It’s like coming up today with a different way to count nutrients from calories, technical merit won’t make it prevail over the whole world that has been built around calories.

johntb86 4y ago

The paper mentions that "In 1995, the World Health Organization (WHO) defined obesity based on a percent body fat ≥25% for men and ≥35% for women [15], while the most recent 2009 guideline [..] used percent body fat ≥25% for men and ≥30% for women". I wonder what the process was for choosing the BMI and obesity cut-points, since they seem to differ a lot.