[CaveTech]

BMI isn't perfect, but it takes height into account. You can actually work back words with her weight and BMI to calculate that her height is less than 5'1".

BMI is pretty accurate most of the time unless you're an athlete. Women putting on far less muscle on average than men, it's far more likely that she was actually overweight...

[Symmetry]

BMI is pretty accurate for heights that were common in 19th century Belgium. It assumes that people's weights ought to go up as the square of their height but as Galileo pointed out back in the day you would expect a person's weight to go up as the cube of their height.

This means that tall people will tend to have higher BMIs all things being equal and short people lower BMIs. Which actually suggests that the woman might have been overweight if she was only 5'1" despite what her BMI said.

[dragonwriter]

> BMI is pretty accurate for heights that were common in 19th century Belgium. It assumes that people's weights ought to go up as the square of their height but as Galileo pointed out back in the day you would expect a person's weight to go up as the cube of their height.

My understanding is that BMI doesn't "assume" anything about what weight "should" do, its instead a measure which has been empirically shown to have a useful (though rather loose) correlation to risks related to various health conditions, particularly cardiovascular conditions. (Mostly, AIUI, it serves as a proxy for a host of other measures, which together are more accurate but more involved to gather.)

The cube-of-height scaling you refer to is what you would expect if taller people were exactly like smaller people but linearly scaled equally in all dimensions -- but that's neither empirically what taller people are built like nor are taller people whose weight relates to that of shorter people that way on average as healthy in the areas BMI is used a risk measure for as the shorter people.