BMI calculations...

TrevorMcC85

Hi everyone,

This has probably already been discussed but I would like to ask those in the know if BMI calculations are accurate?

I have read a few articles recently that speak negatively about them, even going as far to say that they are completely pointless.

I'm just starting out trying to get fit and healthy and am wondering is it a good measurement of where I am and where I would like to be?

Any help would be appreciated!

Trevor

stevencloser

The people for whom it is truly useless know it is useless for them, because they spent years gaining lean mass which makes them a higher BMI at the same bodyfat amount than normal people.
Those people are few and far between though. For everyone else, the healthy BMI range is a good goal to get to when trying to lose weight.

NorthCascades

BMI calculations are very accurate, they can pinpoint your BMI with lots of exactitude. What's not very exact here is what that means. Bigger people have higher BMI numbers and smaller people have smaller numbers; the great controversy is whether people with high BMIs are all muscular demigods, or if any of them might be fat too.

kristen6350

I believe they are accurate for 95% of the population. Lots of people don't "think" it applies to them, but usually it does...unless you have a very low body fat percentage and are very muscular.

When I was 5'11 and topped the scales at 193, I was convinced I wasn't that "big", 27 Overweight BMI, yeah whatever. I was tall, proportionate and big boned. Then I lost weight. Got to 143 at one point. A size 16 US to a size 4 US. Trust me, I was "THAT" big...LOL

Spook_Skywalker

stevencloser wrote: »

The people for whom it is truly useless know it is useless for them, because they spent years gaining lean mass which makes them a higher BMI at the same bodyfat amount than normal people.
Those people are few and far between though. For everyone else, the healthy BMI range is a good goal to get to when trying to lose weight.

This ^^^^^

and..

I use to think it was a crock and that I was a naturally bigger person. Then, I got to my goal weight and realized the BMI chart had me at overweight still and somewhat close to obese. Since then I've lost another 30 lbs and I'm in the "optimal" zone now, but I could even lose another 15 pounds or so no problem. There are people with bigger bones/frames, but that should only account for a very minimal amount of weight and that's why the BMI has different levels within the optimal zone.

GaleHawkins

TrevorMcC85 wrote: »

Hi everyone,

This has probably already been discussed but I would like to ask those in the know if BMI calculations are accurate?

I have read a few articles recently that speak negatively about them, even going as far to say that they are completely pointless.

I'm just starting out trying to get fit and healthy and am wondering is it a good measurement of where I am and where I would like to be?

Any help would be appreciated!

Trevor

@TrevorMcC85 welcome to MFP forums and best of success.

Personally I found BMI calculations a very helpful motivator and it is a read out on my set of bathroom scales. Two years ago my scales and web calculators reported a BMI of 35. As the pounds dropped so did the BMI readout. I remember the day it hit 29.9 so I was no longer classified OBESE by the government guidelines.

At best BMI is a relative measurement without concrete meaning from person to person as to where one has super health or not. My change in my Way Of Eating is to manage my arthritis pain and a side effect has been losing 50 pounds, 40 years of serious IBS and most of my pain. Actually I have developed some muscle without trying. While I do walk at least a 1/4 mile daily with most of my pain gone I do move more and walk faster now as well as being able to get in and out of cars unaided unlike 2 years ago.

sijomial

It's a good guideline for many and inaccurate for a few - that's how population measures work.

But far too many think they are one of the few!

lemurcat12

You might want to check out this thread: http://community.myfitnesspal.com/en/discussion/10438075/how-do-we-judge-a-healthy-weight-range-bmi-is-no-longer-valid#latest

(And what sijomial said.)

aashwill

It is generally accurate.

During discussions online, anyone who thinks it does not apply to them should have to accompany their post with a photograph of them in their swimwear.

GottaBurnEmAll

I have yet to see, in my day to day living, scores of The Rock-like beings running around in the general population that reading various threads on BMI would lead me to believe exist in the world today.

In other words, yeah, what sijomial said.

mumblemagic

This article explains the stats on bmi accuracy as regards a measurement of over-fatness.

TL;DR BMI is not the best measure of over-fatness and the cut-offs as they are have a tendancy to *under*-detect over-fatness. However, there are health risks of having a high bmi even if you have a low body fat. So, if you have a high bmi losing weight could be good for you regardless of fatness, and you shouldn't lull yourself into a false sense of security if you have a low bmi because you could still be over-fat.

http://evidencebasedfitness.net/lack-of-basic-epidemiology-knowledge-makes-us-all-dumber/

JDixon852019

For the majority of the population it is accurate. I notice typically those who scream "BMI is BS" are clearly overweight and in denial about it. For average non-athletes it is pretty accurate.

robininfl

mumblemagic wrote: »

This article explains the stats on bmi accuracy as regards a measurement of over-fatness.

TL;DR BMI is not the best measure of over-fatness and the cut-offs as they are have a tendancy to *under*-detect over-fatness. However, there are health risks of having a high bmi even if you have a low body fat. So, if you have a high bmi losing weight could be good for you regardless of fatness, and you shouldn't lull yourself into a false sense of security if you have a low bmi because you could still be over-fat.

http://evidencebasedfitness.net/lack-of-basic-epidemiology-knowledge-makes-us-all-dumber/

Yes, exactly. BMI is inaccurate, but not in the direction people assume. You are more likely to be overfat without being overweight, than to be overweight without being overfat.

bracey100

I wud rather have a low bmi than big so it's fairly accurate everyones different

Chadxx

BMI is all but worthless. It is supposed to be a reasonable estimate of a healthy level of body fat and in that regard it BS. There are lots of unhealthy people at a "healthy BMI" and you don't have to look anything like the Rock to be at an overweight or even obese BMI, particularly men. If you want to know if you are healthy, look in the mirror, actually check your body fat, check your blood pressure, check your cholesterol, etc.

AnvilHead

Chadxx wrote: »

BMI is all but worthless. It is supposed to be a reasonable estimate of a healthy level of body fat and in that regard it BS. There are lots of unhealthy people at a "healthy BMI" and you don't have to look anything like the Rock to be at an overweight or even obese BMI, particularly men.

I'll save you some trouble - this was already hashed out at length in the previous BMI thread here, complete with a few special snowflakes who were convinced that BMI didn't apply to them: http://community.myfitnesspal.com/en/discussion/10438075/how-do-we-judge-a-healthy-weight-range-bmi-is-no-longer-valid#latest

Chadxx

If it makes you feel good to throw around terms like special snowflake to insult people, go right ahead. I have seen the threads. I have seen plenty of people for which BMI absolutely not an accurate measure of health. What I have never seen is BMI take into account body fat or blood pressure or cholesterol or even something as simple as waist size. Heck, a waist size chart would be better than BMI.

Packerjohn

Chadxx wrote: »

If it makes you feel good to throw around terms like special snowflake to insult people, go right ahead. I have seen the threads. I have seen plenty of people for which BMI absolutely not an accurate measure of health. What I have never seen is BMI take into account body fat or blood pressure or cholesterol or even something as simple as waist size. Heck, a waist size chart would be better than BMI.

The waist-height calculator is good tool, may very well be better than BMI. That said, there is a little difficulty getting the waist measurement at the right spot. Also, I would assume for 90%+ of the population (the exception being the well muscled) both measures would give the same result.
http://prowellness.vmhost.psu.edu/prevention/understanding_risk/whtr

crzycatlady1

Chadxx wrote: »

If it makes you feel good to throw around terms like special snowflake to insult people, go right ahead. I have seen the threads. I have seen plenty of people for which BMI absolutely not an accurate measure of health. What I have never seen is BMI take into account body fat or blood pressure or cholesterol or even something as simple as waist size. Heck, a waist size chart would be better than BMI.

In my own experience BMI matched what was going on with my health. When my BMI was in the overweight category I was unhealthy with a high glucose number and not so great cholesterol numbers. As my BMI went down (ie I was losing weight), my blood panel numbers improved. Now I'm in the healthy BMI range and I also have excellent blood panels, great blood pressure etc. This may not be the case for everyone but it was for me at least.

stevencloser

Chadxx wrote: »

BMI is all but worthless. It is supposed to be a reasonable estimate of a healthy level of body fat and in that regard it BS. There are lots of unhealthy people at a "healthy BMI" and you don't have to look anything like the Rock to be at an overweight or even obese BMI, particularly men. If you want to know if you are healthy, look in the mirror, actually check your body fat, check your blood pressure, check your cholesterol, etc.

Yeah, it's so easy to be obese by BMI without being overfat, a 6 foot person would just have to be 220 pounds, putting them at least at 24 FFMI, and that's when you're at 20% bodyfat which is hardly the best bodyfat amount to have. That goes up to 26 if you go with an actually healthy bodyfat range. 25 FFMI is what's regarded barely still doable by people with great genetics. But yeah tell yourself so many people at healthy bodyfat amounts can be up to obese without that crazy amount of muscle.
I swear, the skewed perception perpetuated thanks to pro bodybuilders is gonna be the death of my sanity.

Chadxx

stevencloser wrote: »

Chadxx wrote: »

BMI is all but worthless. It is supposed to be a reasonable estimate of a healthy level of body fat and in that regard it BS. There are lots of unhealthy people at a "healthy BMI" and you don't have to look anything like the Rock to be at an overweight or even obese BMI, particularly men. If you want to know if you are healthy, look in the mirror, actually check your body fat, check your blood pressure, check your cholesterol, etc.

Yeah, it's so easy to be obese by BMI without being overfat, a 6 foot person would just have to be 220 pounds, putting them at least at 24 FFMI, and that's when you're at 20% bodyfat which is hardly the best bodyfat amount to have. That goes up to 26 if you go with an actually healthy bodyfat range. 25 FFMI is what's regarded barely still doable by people with great genetics. But yeah tell yourself so many people at healthy bodyfat amounts can be up to obese without that crazy amount of muscle.
I swear, the skewed perception perpetuated thanks to pro bodybuilders is gonna be the death of my sanity.

First of all, you skipped the overweight range entirely. Secondly, use whatever calculations you want but it really isn't that hard to exceed the normal or even overweight BMI ranges and be healthy. Last time I lost weight, I was still considered obese according to BMI charts but had abs showing and a 32" waist. That was after only 3 months back in the gym. A couple of guys I work with have 6 packs and are both overweight according to BMI and one of them can't even bench 300. I would hardly call that a bodybuilder.