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.

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

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.

Get a pinch test if you really want to know.

That's what I was gonna say!

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

*white/caucasian body standards too

So Hefty is Helty, right?