BMI

Gurlzie1

Why is BMI used as a measure by gp's and doctors in the army, navy etc if it doesn't allow for muscle mass?

tribulus

Well my BMI was 26. something and it was no problem for applying for the above. They only whip out the calipers if it's over 30 generally so it does take into account those with muscle in this instance.

g'em

Gurlzie1 wrote: »

Why is BMI used as a measure by gp's and doctors in the army, navy etc if it doesn't allow for muscle mass?

GP's use it because it's easy. No body fat measurements needed, no messing around with tape measures, just height and weight required. While it's not very accurate, for the general population it's a handy tool to indicate an aspect of someone's health.

bwardrop

It is a very useful tool when working with large populations, just not foolproof with individuals. There is no problem using BMI on an individual, provided that some common sense is used - i.e. if you have 2 people in front of you who are 6 foot tall and 20 stone, their BMI will be the same. However, if you can tell from looking at them that one is a bodybuilder type and the other is just fat, then you should not interpret the BMI result the same way.

I've given this example numerous times in various posts - if you used BMI to examine 1000 people and determined that 18% were obese, you would probably be correct - 18% will be obese. However, if you go back and use another measure that does take into account body composition (e.g. skinfolds, DEXA, BIA, BIS, MRI) on the same 1000 people, you will probably find that:

a) Some of the people classified as healthy / normal by BMI will have high % body fat
b) Some of the people classified as overweight / obese by BMI will have low % body fat

In general though, BMI is fine. There are exceptions to this (and every) rule. BMI can wrongly classify people:

- those who are heavy but lean will have a high BMI
- those who are light but fat will have a low / normal BMI

It works both ways. However, for the vast majority of people, BMI will be reasonably accurate.

There are problems with all methods of interpreting weight / body composition as they are all only estimates. The only way of measuring muscle / fat / bone mass is through dissection - not really helpful if you are still alive!!

Hanley

Gurlzie1 wrote: »

Why is BMI used as a measure by gp's and doctors in the army, navy etc if it doesn't allow for muscle mass?

Because like others said, it's simple and targets the general population.

Next time you're out shopping, have a look around and see how many heavily muscles people you see who'd get a skewed BMI reading. It's not all that high.

Hell even on this forum I don't think there's a massive percentage of people who'd have a BMI reading of "obese" unless they were actually carrying quite a bit of fat too.

rubadub

Gurlzie1 wrote: »

Why is BMI used as a measure by gp's and doctors in the army, navy etc if it doesn't allow for muscle mass?

Most are not overly big. I would pass most military strength PFTs with ease, (probably not the running though!).

tribulus wrote: »

They only whip out the calipers if it's over 30 generally so it does take into account those with muscle in this instance.

And a military doctor would certain not be as woefully ignorant as some GPs. Also a BBer at BMI 30 may have difficulty in passing some PFTs, since many involve bodyweight. I wonder how many full chinups Ronnie Coleman could do.

dave80

rubadub wrote: »

And a military doctor would certain not be as woefully ignorant as some GPs. Also a BBer at BMI 30 may have difficulty in passing some PFTs, since many involve bodyweight. I wonder how many full chinups Ronnie Coleman could do.

ive a BMI of about 31ish, wat sort of bodyweight exercises do they do and wats the standard?

tribulus

http://www.boards.ie/vbulletin/showthread.php?t=2055326446

It was mentioned in that thread, it's pretty easy but bare in mind it's the absolute minimum required just for entry.

There was no chin ups, just press-ups and situps.

dave80

ye there not very high, could prob bang out double that with no prob

tribulus

They're pass or fail, you're told to stop once you reach the number.

rubadub

tribulus wrote: »

It was mentioned in that thread, it's pretty easy but bare in mind it's the absolute minimum required just for entry.

Yes they are low. I thought the OP was talking of military doctors in general. In the US I think the min is 3 pullups (chins or pullups), but then certain divisions are more, I htink some are 20 min pullups. You can get various PFTs standards online.

It is the minimum and there for good reason. I remember applying for engineering and people in school moaning "thats not fair, you have to do honours maths before you can even apply"- yeah well if you cannot get a B or C in honours maths there is no point in even trying! you will not be able to handle the far harder maths later in the course, you are wasting your time.

No offence to anybody, but if I was fat & unfit and could only barely scrape a pass in the

mile in 11 min,20 push ups in a min and 20 sit-ups in a min

Then I would seriously consider a different career. Unless you have a specific "non-fitness" job in mind.

tribulus

It's 1.5 miles in 11 minutes 30 seconds.

When I did them surprisingly several people failed the run. One also failed the push-ups.

miss no stars

the type of situp they do leads to a lot of failure. Don't forget, other factors can cause people to fail on the day. Everyone's had a bad day where their body isn't working fast, if you're unfortunate, it's the day of your fitness test (I passed mine). The army aren't all that understanding or compassionate when you're trying to ask for a different date. Remember, this is not the fitness test that DF members pass on an annual basis. The annual life test is slightly harder and is graded from 1 - 4 (lower grades exist but are fail grades). Scraping a grade 4 well... get out and work a little harder. Don't get a grade 3... forget about any career courses you might want to do.


as for army doctors being more understanding, if you're overweight grand. Underweight forget it! Note, their definition of underweight is a BMI of under 20, not the standard 18.5-19.5 seen most places. If I'm fit at the time (generally am if I'm about to go to a fitness test) I struggle to get my BMI into that range (18.5 and above) so I will vouch for their lack of understanding.