Think BMI is bogus? Find out why!

beautifulstronghealthy

After wondering why BMI was so screwed up for me and knowing that it couldn't possibly be right, I talked to a personal trainer to see what she thought I should look at. She recommended going by the body fat % rules that I used below. Try it and compare yours!

Comparing body fat % versus BMI:
My lean body mass (bones, organs, and muscle) are 126 lb, according to multiple body fat % tests that I've taken at intervals throughout my weight loss. That is WITHOUT any fat on my entire body. Calculating these % is done by using this formula:
leanlb=weight*(100%-%fat)
weight=leanlb/(100%-%fat)
So at 192 lb with 34% body fat, I calculated leanlb=192(100%-34%)=126

BODY FAT % RULES:
Essential fat 10-13% (required to live) is 140-145 lb
Athlete 14-20% (considered underfat) is 147-158 lb
Fitness 21-24% (ideal) is 159-166 lb
Average 25-31% is 168-183 lb
Obese 32% is 185 lb

BOGUS BMI RULES:
Underweight = <18.5 is 115 lb
Normal weight = 18.5–24.9 is 115-155 lb
Overweight = 25–29.9 is 155-186 lb
Obesity = BMI of 30 or greater is <186 lb

So basically what BMI would tell me is that while I'm in the ideal fitness range or average range of body fat % rules, the BMI will always consider me overweight. So the only way I can be in the normal BMI range is to be underfat and drop a bunch of muscle mass. I wouldn't be considered underfat by BMI rules until I dropped down to 115 pounds, which would mean that I would have to lose 34 lb. of muscle to get there. Ridiculous! FYI, my goal is 160 lb.

lvtruu1

You may be making some assumptions. How do you actually know what your BF% is? No test is perfectly accurate. Also you seem to have assumed that you lost only fat. Far smarter people than myself figure that for every 4 pounds of fat you lose, you lose about 1 pound of LBM.

How tall are you?

All that being said, BMI is a functional number for the masses. Yes it doesn't work well in some individual situations do to large amounts of Muscle. In those cases measurements would be better or a body fat test.

Yes, if you can accurately measure your body fat percentage, than that is the best way to go, but know that even the best tests can be off 5% or more. BMI is a general guild line but from what I've seen many don't want to believe the truth.

In general, I think that most people simply think that being overweight is normal these days. Not to say that 160 isn't the right number for you. I don't know your stats or how current your photo is. Really it is about how you feel and what you desire. If you don't want to be as thin as the BMI chart indicates, then ignore it.

Reading your last paragraph again, seems to imply that you are under 5'5". So you think that 160 at that height is your ideal weight? I don't have the time, but I also think there may be an error in your BF calculation which very likely stems from an over estimation of LBM. Over estimating LBM is universal, better than 95% of people are dead wrong about how much they actually have.

lvtruu1

For example,

I thought that 220 would be a good weight for me, when I was 275. I reached 220 and was still overweight on BMI and was still clearly fat/overweight. I figured 205 the upper limit of the BMI chart would be good. Got there, and found no, I was still heavy. 180 and I still have fat around my waist. I stopped cutting weight figuring that I was getting to thin. But am I? Still 15.5% BF according to Fat to Fit. 11.7% according to hand held device set on normal. At some point I calculated my LBM along the way and it continued to drop as I lost weight. Now that could be that I went the drastic method and lost the weight fairly quickly and did a lot of LISS cardio at the same time. But it is what it is.

What ever weight you decide that you want to be at, is great. It is all up to you. If you think that 160 is appropriate, who are we to argue with you? Obviously you won't be a stick thin model, but that isn't the goal for most people anyway. The insurance industry and the government have to have some way to judge a population and BMI, is and has been a fairly accurate system. Is it perfect? Of course not but it is close enough.

time4changexx

+ your lean body mass will change along the way... Your weight may go down along with fat but your lbm will go up (not just from muscle either; water, blood volume, bone mass) those things change, why overcomplicate it? Seems like your trying to make the numbers easier. At the end of the day its not about the numbers its how you feel. Can you run around the yard with your family and not be ready to pass out? Do you like what you see in the mirror? Are your labs good? Then what different does what some chart tells you?

Carmella9

It's well known that bmi does not take into account body muscle I.e a weight lifter will undoubtedly have a high bmi however there muscle mass will be shown in his/hers body fat percentage (probably excellent)bmi calculations are one way of showing people an approximate of healthy however u say u would have to drop to 115 to be a healthy weight, this is not true as it says your ideal weight should be between 116-155 so anything between this is fine. What I suggest is you strive to have a good body fat % and not worry to much about bmi it is just an estimate used for people that are not to clued up on health and fitness.

AABru

Any tracking device is useful; if you are showing a general downward trend, then you are losing something.

I had my lean mass tested and it was 137 (I used to powerlift and carry a lot of muscle for a woman). I estimate it to be about 130-135, and have based my goal weight of 165 on this. 165 will put me between a size 10 and 6 depending on the brand of clothes, which I think is appropriate for my lifestyle, my husband and my self confidence. Ultimately, as time4change and lvtruu1 said, it depends on how you feel. What works for you? You have to know yourself...:drinker:

mike_ny

Assuming BMI is supposed to be an approximate measure of body fat, both my scale that measures body fat electrically and skin fold calipers using a few different calculations from different body areas are all consistently a lot lower compared to BMI. Even the body fat calculators that just use use wrist measurements along with other body measurement come in lower than BMI.

I'm convinced that the only way to have a healthy BMI number is be very thin and still not have very much muscle mass. So, skinny people out of shape can get passing BMI numbers, but healthy people who work out a lot are doomed to fail.

For me to actually have the BMI number I'm supposed to have for my height, I'd have to weigh no more than my current calculated Lean Body Mass. So, keeping the same LBM, I'd have to have ZERO body fat to have a BMI of around 21 which is abut the middle of the "normal" range for BMI. Or, I'd have to lose almost 20 pounds of muscle and LBM. Either of those options is ridiculous.

lvtruu1

Assuming BMI is supposed to be an approximate measure of body fat, both my scale that measures body fat electrically and skin fold calipers using a few different calculations from different body areas are all consistently a lot lower compared to BMI. Even the body fat calculators that just use use wrist measurements along with other body measurement come in lower than BMI.

I'm convinced that the only way to have a healthy BMI number is be very thin and still not have very much muscle mass. So, skinny people out of shape can get passing BMI numbers, but healthy people who work out a lot are doomed to fail.

For me to actually have the BMI number I'm supposed to have for my height, I'd have to weigh no more than my current calculated Lean Body Mass. So, keeping the same LBM, I'd have to have ZERO body fat to have a BMI of around 21 which is abut the middle of the "normal" range for BMI. Or, I'd have to lose almost 20 pounds of muscle and LBM. Either of those options is ridiculous.

You may be viewing the chart incorrectly. It isn't about being in the "middle" of the range. The range covers different body types. Super skinny people would be at the lower end, and thicker people would be at the upper end. The chart is used to determine if a person is at an appropriate weight. It doesn't mean that they are in shape, just means they fall in a range that suggest that they are probably in okay shape. It was invented to give the insurance/government a way to gauge a population from a number. Of course it doesn't apply to everyone. Of course many people fall into the range and are in woeful shape but on average, over a huge number of people, it is appropriate. For you, maybe it doesn't apply.

I fear that telling people that it is okay not to fall within that range is usually a mistake. If you tell someone that it allows them to feel fine carrying extra weight that isn't necessarily healthy. You could go to your doctor and ask directly what they think and how much weight they think that you should lose if any.

Most people usually over estimate their LBM as well.

beautifulstronghealthy

Wow. I didn't expect so many people to be so convinced that bmi is really accurate. I'm actually 5'6" and very muscular. As I said, I've been watching lbm through a 50 lb weight loss. I work out 6 days a week and am extremely healthy according to my doctor. I am a size 12 at 190 pounds and expect to be about a size 8 at my goal weight. That is NOT "carrying around extra unhealthy weight". I have done body fat % tests with a personal trainer. I have consulted my doctor who agrees with my goals and assessment of what's healthy. Additionally, at 20% body fat I would never consider someone to be fat. I don't think my doctor would worry if bmi said I was overweight but my body fat was 20%. Come on. I'm just pointing out that there are other tests to consider when determining what's healthy for each person.

My point in writing this was not to make excuses for unhealthy lifestyles because I eat clean and really healthy and I exercise a lot. My point was to tell people to re-examine what the "rules" are because they may not be as clear cut as they seem. I am confident in myself and just wanted to help others who may feel like the numbers just don't add up.

boboff

But it is only that a number.

No one likes to be called Obese mind, I don't, but then I am!

I agree with what allot of people here have said, it's what makes you happy that is important, and the numbers are not.

BarackMeLikeAHurricane

You'll lose lean tissue as you lose weight. It won't necessarily be from muscle though. As you get lighter your body doesn't need all of the extra connective tissues to support excess weight so your body breaks it down.

wnbrice

Every single person I have talked to about it from doctors to trainers have said that "Alright your BMI is high, but looking at your this percentage is gonna be off"

LJSmith1989

Wow. I didn't expect so many people to be so convinced that bmi is really accurate. I'm actually 5'6" and very muscular.

Lmao, you cocky bugger. You say that there are other tests to consider but then you have only examined body fat %...

To be fair though you have to use what ever tools are useful to you. So if bodyfat % is most useful then good for you.

Docmahi

the more lean muscle mass you have the more inaccurate BMI is - its as simple as that

I have never walked into a patients room with an overweight BMI and talked about weight reduction right off the bat - its just a number people need to quit getting so tied up with it

beautifulstronghealthy

Lmao, you cocky bugger. You say that there are other tests to consider but then you have only examined body fat %...

To be fair though you have to use what ever tools are useful to you. So if bodyfat % is most useful then good for you.

Well, I'm a little irritated. I'm not actually cocky.

I've actually done other tests in the past, but only quoted the most recent ones. My original goal was actually lower, but my personal trainer looked at it with me and decided it would be too low. And for the record, I have a sister who is built similar to me and her BMI is in the healthy range, but she is emaciated and looks terrible because getting sick and losing muscle was the only way for her to get to her current weight. Now she works out and has put on a little more muscle, but yuck.

I didn't write this post because I needed people to congratulate me. Like I said, I just wanted others to know they have other options to consider as well. Thank you to all of you who have been positive and supportive.

beautifulstronghealthy

the more lean muscle mass you have the more inaccurate BMI is - its as simple as that

Exactly.

LJSmith1989

Lmao, you cocky bugger. You say that there are other tests to consider but then you have only examined body fat %...

To be fair though you have to use what ever tools are useful to you. So if bodyfat % is most useful then good for you.

I've actually done other tests in the past, but only quoted the most recent ones. My original goal was actually lower, but my personal trainer looked at it with me and decided it would be too low. And for the record, I have a sister who is built similar to me and her BMI is in the healthy range, but she is emaciated and looks terrible because getting sick and losing muscle was the only way for her to get to her current weight. Now she works out and has put on a little more muscle, but yuck.

I didn't write this post because I needed people to congratulate me. Like I said, I just wanted others to know they have other options to consider as well. Thank you to all of you who have been positive and supportive.

I doubt it was the BMI that encouraged your sister to look the way she did, just poor eating and general habits. Like you say yourself BMI shouldn't be the only tool people use. I doubt it is.

Spokez70

Yep- I had a DEXA scan done in January which said I have 190lbs of LBM- which is only 9lbs away from being "Overweight" according to BMI at my height. I'm not really interested in getting to 199 for that.

ptjolsen

Your trainer is right....you have a good one....I wish more people would understand this.

WendyTerry420

I agree. Body fat percentage is WAY more important than scale weight.

traceytwink

Your trainer is right....you have a good one....I wish more people would understand this.

I agree, my doctor also told me body fat was the better test and not to worry too much by the bmi, think its about time the guide lines were changed