Comment by FeteCommuniste
11 days ago
> The most notorious of which is BMI; it is practically a category error to infer someone's health or risk by individual BMI, and yet doing so remains widespread amongst people that are supposed to know better.
BMI works fine for people who aren't very muscular, which is the great majority of people. Waist to height ratio might be more informative for people with higher muscle mass.
As a person who has been told I'm "morbidly obese" for decades now, I will say that doctors at almost every level look at your chart not you. I've been told time and time again that until I get my weight under control, my health will suffer.
I'm 5'8" and weigh on average 210lbs. My BMI isn't even morbidly obese, it is 31, which is just "regular" obese, but on top of that, a DEXA scan shows that I am actually only 25% body fat, with only 1lb of visceral fat.
Doctor's don't care about that, they see on the Epic chart that my BMI is > 30 and have to tell me some spiel about a healthier lifestyle so they check check off a checkbox and continue to the next screen.
I'd consider 5'8 and 210lbs morbidly obese. An average male at 5'8 should generally weigh about 150lbs and no more than 164lbs.
> I'd consider 5'8 and 210lbs morbidly obese. An average male at 5'8 should generally weigh about 150lbs and no more than 164lbs
You would consider incorrectly then.
This person has ~155 pounds of lean body mass. 164 would put him at roughly a body builder level of fat, which basically requires a part time job in cooking and nutrition to maintain.
For reference, I’m in a similar situation to this person. I’m 5’11” (180cm) and about 200 lbs (91kg) with about 170 lbs of lean body mass. My dexa scan says that I’m 15% body fat, but I get the same lectures from doctors about being obese and needing a lifestyle change, all based on BMI and (I assume) my size (I’m barrel chested). It’s completely absurd.
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If I got rid of all of my fat and bones, I'd still weigh more than 150lbs. I have the most muscular 150lbs man inside of me.
Ideal body fat percentage is 18-24% - I'm at 25% (or was in November - might be +/- 2% since then - gained a few pounds weight, but not waist size).
So I would say I'm not morbidly obese or even regular obese based on the percentage of my body that is muscle vs fat.
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Or that guy could be a burly bricklacker / concerete worker who can casually carry hundreds of pounds of weight all day every day in brutal conditions.
It's really hard to tell with the data provided.
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Huh. The standard in your case is to measure waist circumference if BMI is high. Did no doctor do that? As long as you are below 40” or 37” if Asian you are considered good to go.
None ever did.
On top of that, I'm not sure if that is a real indication of anything, either.
The reason to do that is to get an idea of your abdominal fat (which is the more dangerous place for fat to store), but there are two types of abdominal fat, one is dangerous (visceral fat) and one is completely benign (subcutaneous fat). And a measurement around your waist won't tell you which you have.
I personally have almost all of my fat subcutaneous, with only 1lb of visceral fat (which is right in the perfect range).
> Doctor's don't care about that
Literally all of them?
When humans talk, they use generalizations (and don't need to annouce them). Here it means that most doctors don't care about that.
Follow that rule next time you read such a statement in a context that's not formal math.
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I can't say literally all, but in my experience with having to get a new GP almost every year because of health insurance changes, location changes, hospital consolidation buying my GPs practice, and multiple doctors retiring or just quitting medicine (my last GP was tired of medicine after practicing for only 3 years). Over the last 20 years, I've had almost 15 GPs across 5 states (NY, NJ, CT, TX, LA). I also have multiple auto immune diseases, so I have had a handful of specialists of various flavors (endocrine, oncology - not for cancer, cardiology, and urology), but only need them occasionally.
Almost every single start of every single appointment (including a follow up from just a couple days prior), they comment about my BMI. It is the rare time they don't that I remember. My last urology appointment the doctor was very congenial, didn't even go over the lab work, just said, everything is looking good, asked how I was feeling, everything good, alright, refilled my prescriptions and left.
I mean those stats arent good...
No. BMI does not work as a diagnostic measure for general population. The range of "normal" BMI values does depend at least on genetic lineage, gender and individual development history. Fine to compare two scandinavian lineage men, but if you compare e.g. a dutch man with an african woman oh boy, you error margins would be mid-to-high single digit units
> Waist to height ratio
Again, while not a bad metric per se, translates poorly between cohorts.
My understanding is that it doesnt even do that, because it creates false negatives for the so called skinny fat body type: significant visceral fat mass, which is what we are concerned about, but not much muscle or peripheral fat mass, thereby not being flagged by BMI screens, even though they are at risk.
> BMI works fine
An individual learns nothing from its calculation and it has no clinical value. I receive more constructive feedback from an auntie jabbing me in the chest and saying "you got fat".
> the great majority of people
There is wide morphological variety across human populations, so, no.
I dunno, basing life decisions off a metric that has a fudge factor built into it to make the regression work feels sub-optimal to me.
BMI underestimates in most cases and your body fat is higher then the chart would predict.
When people say "oh BMI isn't accurate" it means you are more overweight then it suggests unless you are literally an extreme body builder.
This underestimation has a name, "Normal Weight Obesity." Known by the slang "hot guy/girl fit" where the person looks like they would be physically fit because they're skinny but there's no muscle under there.