> screening tool

People tend to think in absolutes. Even perfectly rational people fall logically foul to not considering outliers.

Yeah, people don't want to understand that your body structure messing with BMI is quite real but only a few points. It's unquestionably "wrong" in scoring me higher than my wife despite the fact that she's the one with a few extra pounds. But it scores us both as normal, the difference doesn't matter.

Anything to pretend they aren't too heavy.

>Getting all the way to the obese BMI range while having healthy body fat is only happening for people with an extreme dedication to body building and diet

And sumo wrestlers.

The line seems to be drawn at (effortful) activity level more than anything else. And BMI doesn't say anything about that.

I think the vexation comes from the focus on an attribute that is not directly mutable, per one's agency, because that's easier to sell things related to. Versus action that you have a lot more direct control over (social or physical circumstances notwithstanding).

The farther from average height you are the worse it is. If you are from some part of the world where the average height distribution is near the point BMI based itself you will perceive it to be so much better.

I am only 6' and only an intermediate lifter. I'm overweight, but BMI makes me look obese. It really only takes a normal person a year or so to get to three plates on squat with no supplements other than chicken broccoli and rice if they don't skip workouts. Assuming no injuries. That level of strength easily distorts bmi wildly if you are even a little taller than average.

> Many active gym people have pretty high BMIs but fairly low fat

I think this is greatly exhaggerated.

Yeah you can put on as much muscle as Arnold and have a FFMI of about 27 then maybe have a BMI of 34 if you have 20% body fat.

But a very gifted natty might cap out at maybe 24 with a BMI of 30 at 20% bodyfat. But let's be realistic. This is not "many active gym people". This is the guy winning the local strongman meet.

Yes a couple of years training for most people can add a couple of points to BMI but I think people exaggerate how much this is. Go look at a 20lb brisket at costco - you don't see people with that much extra muscle all that often.

> Many active gym people have pretty high BMIs but fairly low fat (because muscle is dense),

I’ve been in the overweight BMI category with low body fat by being active at the gym and focusing on diet. It takes some work to get there.

If I check the calculators for the obese BMI range, there was no way I could get there without either gaining a lot of fat on top of the muscle. The amount of muscle required to have an obese BMI with healthy amount of fat is absurd.

I believe evidence points towards absolute level of fat being more important than % for overall health.

E.g. 20% bodyfat at 250lbs is still a lot of fat.

Of course it's difficult to ever get very high on absolute fat if at 15% or below.

If bmi says you're obese, you very likely (~95%) are. The problem is that bmi only catches about half of people who are obese.

https://www.nature.com/articles/s41598-020-69498-7

It's not really intended to be applied to individuals at all, but if you're in the "healthy" BMI range then you are probably fine just not thinking any further about your weight and doing something like measuring your body fat percentage would just be a waste of time and a source of stress for some people. If you're outside that range, then it is worth doing some of the more involved things to judge if your weight is healthy.

It’s a tool not the tool. If you have obese BMI you can… look in the mirror and see how accurate it is. If you aren’t sure take one of the dozens of other tests. People focus too much on it being a one stop shop - it’s not. It’s the start of a dialogue with your pcp and self on assessing your health that’s highly correlated with poor health outcomes.

It isn't accurate. It is a statistical tool meant for easily measuring populations of people. It does not apply in any meaningful way to individuals.

Which for the majority of the population isn't relevant.

The people most obsessed with "BMI isn't accurate" are overweight people making excuses for themselves.

A muscular person can be "overweight" by BMI standards but not overfat at all. This is the case for many types of athletes, specially in strength disciplines but not only. It is the case in the fitness world that people ignore BMI and are intesterested in body-fat-percentage instead. This is hard to measure accurately so not so useful metric for the general population.

I've been considered borderline or obese by the standard BMI index for 20 years at least, but for a lot of that had very little to no visible extra weight. A lot of that was just plain having more muscle than the average the standards are built around, but I also suspect BMI gets to be really inaccurate for tall people. I would look anorexic if I had to drop enough weight to be considered not overweight.

Not necessarily, a bodybuilder or very athletic person might be overweight in the sense of above average for their height but not overfat.

"Overfat" just refers to having too much fat.

"Overweight" can mean the same thing for weight, but it also refers to those with a BMI specifically between 25 and 30, and those with BMIs greater than 30 are classified as "obese".

The dominant discrepancies are "expected" fat (boobs, etc), and "unexpected" muscle (cyclists, body builders, hard labour careers, etc). I'm currently around 10-15lb overfat and 40-50lb overweight [0]. Only the former statistic matters.

[0] And that, at least somewhat, tracks visual perceptions. Nobody looks at me with a shirt on and believes I need to lose weight, because 10-15lb isn't _that_ much extra on a tall frame. If I were 40-50lb overfat then that would be painfully obvious regardless.