BMI - How accurate?

[W1Z@RD]

I just did my BMI and it comes in at 23.5

 

25 you are considered overweight yet I'm considered skinny by everyone and still wanna lose 6 KG's for the summer cycling season.

 

Do these formula's vary? Are they worth anything?

 

http://en.wikipedia.org/wiki/File:Body_mass_index_chart.svg

 

Am I skinny or is everyone else fat?..

[eddy]

Q: BMI - How accurate?

 

A: Not at all

[Tankman]

BMI is a load of hog wash.

 

Based on your length and weight alone cant be accurate.

 

The taller you are, the more you are screwed.

 

If you are a skinny cyclist at 75kg and 1.85m tall your BMI is 21.9 - "normal"

 

If you are a sprinter cyclist at 90kg and 1.85m tall your BMI is 26 - "overweight"

 

If you are a body builder/rugby player at 110kg and 1.85m tall your BMI is 32 - "obese"

 

All above are fit and healthy.

 

Hog wash, I tell ya!

[W1Z@RD]

Good to know.... Tx guys!

[Bennie Dikwiel]

Mine is 28.1 so I am just out of the "Obese" range and am now in the top end of "Overweight"

I think NOT

[eddy]

Mine is 28.1 so I am just out of the "Obese" range and am now in the top end of "Overweight"

 

Dalk is jy nou Bennie dikpens

 

Ps. thx for the light I bought, it is brilliant !

Edited August 26, 2012 by eddy

[Goodbadugly]

Some of these figures comes from the life insurance business. One good example is the measurement of your abdominal girth. They were looking for a cut off. So if it was more, they could charge you more, because supposedly it makes such a person more prone to dying. This magical figure then being 100cm. So at 99cm you are "safe". More than 105cm is FATAL. Whether you are 2.1m tall or 1.6m. Schwartznegger or Woody Allen

Another sample is that you take your hight in cm's and subtract 100. That is your ideal weight. (For women hight in cm's minus 105)

A BMI just gives you a ballpark figure. Much easier to do than calculating your body fat %. Anybody(well most anyway) with a scale and a measuring tape can do it without screwing up.

[funjunkie]

BMI is not at all accurate in athletes.

 

The information it tells you is your weight in relation to your height.

However, it does not take into account body composition. So for example, if you take 2 people who both have a height of 1.73m. Both weigh 80kg. Their BMIs are 26.6. One is a trained athlete with a body fat percentage of less than 5%. He is all muscle and hence heavy. The other is a lazy slob with a large beer belly and man boobs. They both have the same BMI which is in the overweight range.

 

The more accurate determinant would be body fat percentage. Can be measured by skin calipers. Most dieticians and biokinetists should be able to do this.

Edited August 27, 2012 by funjunkie

[pastapouch]

Just look in the mirror. Are their parts that are hanging. If so, you have problems.

[Zatek]

Just look in the mirror. Are their parts that are hanging. If so, you have problems.

What about the ladies?

[pastapouch]

What about the ladies?

If it isn't the nice parts that are hanging, but usualy if the belly hangs, everything else hangs as well. We call those girls seksie. "Seksie op seksie" LOL

[Mr SingleTrack]

I agree with all the comments. BMI is supposed to only be a guideline. However it is inaccurate because it does not take into account muscle and bone mass.

[seven]

It completely depends on what you want to get out of it.

 

Yes, it doesn't account for muscle mass, but that is not what it was developed and validated for. It comes from long-term epidemiological studies "predicting" your risk of heart problems/strokes/diabetes/etc. It is not developed, and have never been intended to be used by the active/sporting population.

For these intended purposes it is very accurate, and no - it is not simply a way for the medical aids to charge you more.

 

As with all predictive formula, if you are at the extremes of the population (weight/fitness/activity level/height/age/etc) ALL predictive formula will be out. For the average population (and remember the "average" person in SA, and the rest of the world HATES exercise), the BMI is perfect for PREDICTING RISK. THAT is ALL that is good for, nothing more, nothing less.

Edited August 27, 2012 by seven

[jmaccelari]

BMI is rubbish. I have a BMI of 25.4 meaning I am on the obese side. My body fat % as measured is 12-15%. The problem is it doesn't take muscle into account. I am muscular,so heavy for my weight.

 

I brought this up with Discovery as my fitness is top notch according to their fitness test, but I lost points since I am "obese", They are unhappy with BMI (ianj is also obese, apparently!) and are looking at a new measure.

 

I see a new and "improved" measurement is ABSI:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0039504

 

Here's a calculator:

http://absi-calc.appspot.com/

[seven]

Agree with the new formula.. looks like its based on allometric scaling, so it takes out some of the issues with the outer range of the normal population

 

Think it will take some time before this starts being the norm though

[TopFuel]

The BMI system is simply a ratio of weight to height. It does not take what type of weight you put on into account. This is generally not applied to athletes for the above reasons. As most of the hub members are althetes, their BMI is not very accurate due to the disparity created my increased muscle mass. Muscle is heavier than fat. But in a non-exercising group of individuals, it is a useful screening tool for obesity.

 

Take home message: if you think you're overweight, you probably are. You don't need a formula to tell you that.