Why does BMI have units of kg/m^2 when we are three dimensional? Wouldn’t kg/m^3 or g/cm^3 be more accurate?
In: 100
How does one compare how overweight/underweight one person is to another?
It’s not the absolute weight. You have to take height into account.
Turns out height squared works consistently to compare people’s weights over a wide variety of heights and weights.
People’s (volume) cm^3 doesn’t track with their weight as much as the square relationship of height
it’s not really a unit of density, it’s just a mathematical formula that we’ve found correlates decently with someone’s health (specifically to be used as a rough marker for obesity). so yeah in theory if it was density then that would make sense, but the unit just follows the formula which is weight/height^2
Weight over volume would be very close to 1 for everybody.
This formula makes a better number to interpret
it’s not really a unit of density, it’s just a mathematical formula that we’ve found correlates decently with someone’s health (specifically to be used as a rough marker for obesity). so yeah in theory if it was density then that would make sense, but the unit just follows the formula which is weight/height^2
Weight over volume would be very close to 1 for everybody.
This formula makes a better number to interpret
it’s not really a unit of density, it’s just a mathematical formula that we’ve found correlates decently with someone’s health (specifically to be used as a rough marker for obesity). so yeah in theory if it was density then that would make sense, but the unit just follows the formula which is weight/height^2
If it were kg/m^3 then it would just be proportional to density. The idea of BMI is that there is a healthy range of weights for people. Fatty tissue has a slightly different density than lean muscle, but not that different, so BMI wouldn’t be very sensitive if it were just the density.
So, knock off a length factor and you have something that correlates well with fitness. You can think of it like, you get one factor for height, but your girth, you only get one factor even though it’s 2d.
How does one compare how overweight/underweight one person is to another?
It’s not the absolute weight. You have to take height into account.
Turns out height squared works consistently to compare people’s weights over a wide variety of heights and weights.
People’s (volume) cm^3 doesn’t track with their weight as much as the square relationship of height
Weight over volume would be very close to 1 for everybody.
This formula makes a better number to interpret
If it were kg/m^3 then it would just be proportional to density. The idea of BMI is that there is a healthy range of weights for people. Fatty tissue has a slightly different density than lean muscle, but not that different, so BMI wouldn’t be very sensitive if it were just the density.
So, knock off a length factor and you have something that correlates well with fitness. You can think of it like, you get one factor for height, but your girth, you only get one factor even though it’s 2d.
Latest Answers