BMI questions

unkel

The BMI (Body Mass Index) is a measure used a lot these days to categorise people as being overweight or not. I'm sure you all know how to calculate BMI. But just to specify its your weight in kilograms divided by your height in meters square.

According to the index your are:

Below 18.5 Underweight
18.5 – 24.9 Normal
25.0 – 29.9 Overweight
30.0 and Above Obese

Now my point is: this index is not gender specific. I do not understand this. Surely a woman and a man of the same height should not have the same weight to fall into the same category? IMHO the woman in this example would fall into a higher category. Also this index does not take into account what way a person's body type is.

Just some examples:

Brad Pitt and George Clooney are obese according to BMI, and also Arnie Schwarzenegger who at 6"2 and 235lbs (according to a previous post ) when at the top of his bodybuilding career as Mister Universe would be off the scales.

How can someone be overweight or obese when their body fat percentage is low or less than average?

Tried and searched the boards for this but could not find anything.

Maybe Jak has an answer as surely he might be overweight / obese according to BMI?

tunney

BMI can not be blindly applied, a bit of common sense and intelligence is required. Try substitiuting cop-on for whining and I'll think you'll find it works okay.

logic1

For bodybuilders BMI measurement is irrelevant.

The BMI or Quetelet Index was developed in 1981 and today isn't a very accurate measurement of obesity at all.

Basically no one should really be worried about their BMI index as their are much more useful ways of getting an accurate bodyfat measurement.

Under Water Weighing, Magnetic Resonance Imaging, Total Body Water, Total Body Potassium, Dual Energy X-ray Absorptiometry, Bioelectrical Impedance, Near Infra Red Irradiation and Skin Fold Thickness can all be used to a much more accurate degree than BMI.

.logic.

Jak

Aye, Right now my BMI index drops me at 30, or obese.

Also the same for my brother.

The BMI was not developed to deal with bodybuilders or powerlifters even. The reason as far as I'm aware is that it takes into account an average weight of muscle into calculations. Now muscle weighs more than fat ...

(I will instantly ban any halfwit who replies saying a pound of fat is the same as a pound of muscle. Yes we know that is true, but for the space they occupy on the frame, muscle is denser and heavier. For the equivalent weight I *believe* muscle would occupy about 3 times more space. I would love an accurate figure on this though.)

... so when the BMI calculates it takes away average muscle density, average skeletal weight, organs etc ... until it is left with a number which it assumes is lard and gives you a figure.

If you are average it can be an ok guideline, but I've never been accused of being obese and one should never get to concerned over the results from such stock formulas.

Water immersion is the way to go.

JAK.

tunney

Water immersion is the way to go.

Or for some posters a posthumous dissection would be what I recommend.

unkel

Originally posted by Jak
For the equivalent weight I *believe* muscle would occupy about 3 times more space. I would love an accurate figure on this though.)

AFAIK muscle weighs 1100 grams per liter and bodyfat 900 grams. These figures are apparently fairly correct although they appear to be rounded