final examples, BMI/waist-to-height/waist-to-hips

[Guest guest]

You were right, of course; the 5'4 " vs 6'3 " conversion should have been 1.2

instead of 1.1 for the 20-percent difference.

>I think the idea behind using height squared for BMI

>is that cubing the height grossly exaggerates the

>relative volumes of people of different height. As

>you pointed out, measuring hips is difficult.

>Measuring body volume is worse! Especially if someone

>has a fat tummy and skinny legs. Height squared

>approximates the body surface area, which roughly

>correlates to body size and is less wildly sensitive

>to height variation.

Compare a 5' woman (who maybe teaches yoga) with a 6' man (20% taller).

Using weight (in kg) divided by height (in meters) _cubed_, which we'll

call BCI, say the woman weighs 105 (the Goldilocks weight) and has a BCI of

47.62/1.52 cubed = 13.6. She would not be terribly skinny. Her BMI is 20.5.

The guy's corresponding BCI-generated weight would be (1.83) cubed or 6.13

X 13.6 = 183 pounds, which isn't bad for a 6' guy.

His, BMI-corresponding weight, though, would be 151, which would be

_danged_ skinny for a six-foot fellow, and would likely require loss of

lean body mass in getting there.

The 20.5 BMI X 1.2 (the unincluded factor in BMI vs " BCI " ) would be 24.6,

which would yield the same approx. 181-lb 6-footer, which I would suggest

would " look more like " a 105-lb 5-ft person than would a 151-lb six-footer.

I think that if you run likely BF-% numbers on the various cases, you'll

also find that the BF percentages show that BCI is a better metric.

>You're saying that 6' 3 " is 10% taller than 5' 4 " . (I

>would say that 6' 3 " is 10% taller than 5' 7.5 " , but

>let's ignore that for the moment). The BMI=24 for a

>5'4 " person corresponds to 140 lbs.

>The BMI-26.4 for

>a 6'3 " person corresponds to 211 lbs.

>That's a 50%

>difference in weight.

211 on a 6' 3 " guy isn't very heavy, in terms of fat and adiposity, and

probably compares well with the appearance of a 140-lb 5' 4 " person.

However, what I was

>really saying was that since women have smaller bones

>and more body fat, we should shoot for lower BMIs. A

>woman and man of the same height would appear very

>different at the same BMI. The woman would look much

>fatter.

YES! But that's because it's a flawed measurement, imo, and because for a

similar BF, it will give much lower values for a short person than for a

tall person (of the same BF %).

> > Waist to height at least compares a one-dimensional

>measurement (h) with

> > another (2-pi-r) as does waist to hips. Waist to

>hips is probably better,

> > but I think its easier to consistently measure waist

>and height than them

> > pesky hips.

> > ;-)

>

>Nevertheless, the waist-to-height measurement runs up

>against the " DC level " of the lower limit of waist

>circumference --due to the volume taken up by the

>organs, etc. Thus, it discriminates against short

>people!

I haven't considered that one, but heart and brain size are proportional in

three dimensions to height (more body to service). But in any case, waist

to hips seems superior.

Maco