My BMI Says I'm Obese, but Am I Really?

  • Thread starter G01
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In summary: But, for the average person, BMI is not an accurate measure of their health and does not predict their risk for obesity-related conditions.
  • #1
G01
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According to the BMI, I am obese...

The truth is, I am not obese. I am in better physical condition that most of my friends. Since moving to Boston, I don't use a car. I bike and walk everywhere I need to go sometimes with the help of the T. I also train in Judo ~3 times a week, which is one of the best full-body workouts I have ever participated in.

I am in good shape and I eat healthy. My blood pressure is well within the normal range. I don't have six pack abs, but I don't have a beer gut either!

I admit I am a big guy (6ft, 215lbs). I won't be staring in an xkcd comic strip anytime soon. However, I have a higher proportion of my body weight in muscle mass. People who have tried to guess my weight usually guess around 185-195lbs by the way I look.

Can someone in the medical or bio community tell me why the BMI is used when it only accurately describes people who are of average build and do no physical activity whatsoever?
 
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  • #2
G01 said:
Can someone in the medical or bio community tell me why the BMI is used when it only accurately describes people who are of average build and do no physical activity whatsoever?

Because it is used to describe the average POPULATION of people... possibly? By the measurements you gave me you're not obese assuming you're exacly 6' you're BMI is 29.2. Obesity starts above 29.9.

Indication that you are obese is your body fat percentage. If you have over 25% body fat then THAT puts in you the obese range. Obesity is when the body fat accumlated on your body affects your health negatively.

Although just, a small point, because you THINK it's healthy and you're in perfect shape means nothing. Having low body fat percentage is still unhealthy and dangerous.

The BMI is not used to make these judgements. It's used to PROXY. You'll never find a doctor take your BMI and claim you're obese...
 
  • #3
G01 said:
According to the BMI, I am obese...

The truth is, I am not obese. I am in better physical condition that most of my friends. Since moving to Boston, I don't use a car. I bike and walk everywhere I need to go sometimes with the help of the T. I also train in Judo ~3 times a week, which is one of the best full-body workouts I have ever participated in.

I am in good shape and I eat healthy. My blood pressure is well within the normal range. I don't have six pack abs, but I don't have a beer gut either!

I admit I am a big guy (6ft, 215lbs). I won't be staring in an xkcd comic strip anytime soon. However, I have a higher proportion of my body weight in muscle mass. People who have tried to guess my weight usually guess around 185-195lbs by the way I look.

Can someone in the medical or bio community tell me why the BMI is used when it only accurately describes people who are of average build and do no physical activity whatsoever?

I don't actually think we have the medical community to thank for BMI. I think I remember reading that it was once suggested as a hard and fast (and really rough) indicator of obesity and then the popular nutrition movement and media just ran with it. I don't know if it's actually used in the medical community in a serious way at all. It's more fad diet books and stuff which don't have a clue what they're talking about anyways (and government nutritional prescriptions which are the same difference). Could be wrong though. I'm in a quasi-similar boat. I definitely have a bit of fat but I'm also just very large. Like I have very broad shoulders and thick arms (which are pretty muscular). According to BMI I'm on the high end of obese but my body fat index isn't nearly that high.
 
  • #4
But as Sorry! has already pointed out: No doctor would ever use BMI to determine whether or not you are overweight and need to loose weight.
BMI is certainly useful in that a high BMI is ONE risk factor for many medical conditions (e.g. type II diabetes) and is easy to calculate. However, all a high BMI means to YOU is that it might be worth talking to your doctor.
As far as I know the only time BMI is used "scientifically" is for epidemiological studies; i.e. to correlate obesity with certain medical conditions.

There are certainly people that have BMI much higher/lower than "normal" that are still healthy (professional athletes would be an obvious example) and for those BMI is a useless measure, but for the vast majority of us BMI is still a useful indicator.
 
  • #5
At my heaviest, the BMI would have indicated that I was over-weight. However, my fat to body content was low (~5-6%) because I ran long distance (and sprints), played soccer, rode a bicycle for transportation, and did weight-lifting/training. The BMI for a lean muscular person is the same for someone of the same height and mass but higher body fat content.

Sparring or a full-body workout in any of the martial arts is a great workout.
 
  • #6
My body fat percentage is less than 10% and it tells me I'm overweight.
I don't see the point of it, if it can be so wrong for so many people. Body fat percentage however, isn't. Why use anything else?

I like the old fashioned method of finding out if you're overweight; looking in the mirror.
 
  • #7
Sorry! has it right. BMI is used on a population basis, where those who are leaner than it predicts and those who are fatter than it predicts balance out. It's more of an epidemiological tool than useful on an individual basis. That it is useful to tell you anything about an individual is a myth perpetuated by websites with BMI calculators. It's probably useful to some extent for those who really are obese and in denial about their weight, but if you work out and are generally lean and muscular, you can safely ignore it.
 
  • #8
Moonbear said:
Sorry! has it right. BMI is used on a population basis, where those who are leaner than it predicts and those who are fatter than it predicts balance out. It's more of an epidemiological tool than useful on an individual basis. That it is useful to tell you anything about an individual is a myth perpetuated by websites with BMI calculators. It's probably useful to some extent for those who really are obese and in denial about their weight, but if you work out and are generally lean and muscular, you can safely ignore it.

That's makes sense. Though, I still think some people give the BMI more credit than it's worth.

The reason I calculated my BMI in the first place was because a local school is going to start keeping track of BMI to determine whether a student is overweight or obese and inform and guide the parents based on this data. I wanted to see what it would say about me. Unfortunately, this leads me to think that a bigger, yet athletic student may wrongly be told that they are overweight or obese and needs to change his or her body. I think this is probably the last think we want to do to adolescents and children who already are overly concerned with how they look.

Do you guys think the BMI should be used in a situation like this? I think if the school really wanted to positively enforce a healthy lifestyle they would do so through lunch offerings, P/E classes, and by monitoring more accurate measures of one's health. It seems to me the school wants to say they support healthy living while avoiding putting more money into the cafeteria and P/E.
 
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  • #9
G01 said:
Do you guys think the BMI should be used in a situation like this? I think if the school really wanted to positively enforce a healthy lifestyle they would do so through lunch offerings, P/E classes, and by monitoring more accurate measures of one's health. It seems to me the school wants to say they support healthy living while avoiding putting more money into the cafeteria and P/E.
No. If the school is promoting a healthy lifestyle, using the BMI is the wrong criterion. It should be based on cardiac efficiency, HDL/LDL levels, triglycerides, blood pressure, pulse rate when resting, and perhaps other factors.

BMI is just an easy number to use - but its application here would be incorrect for the reasons stated.

My current BMI is 25.7, but I'm not overweight, although the BMI says I'm slightly overweight. I just had a physical and the HDL/LDL numbers and triglycerides were fine, and my blood pressure was ~110/70, which it has been for 40+ years.
 
  • #10
G01 said:
That's makes sense. Though, I still think some people give the BMI more credit than it's worth.

The reason I calculated my BMI in the first place was because a local school is going to start keeping track of BMI to determine whether a student is overweight or obese and inform and guide the parents based on this data. I wanted to see what it would say about me. Unfortunately, this leads me to think that a bigger, yet athletic student may wrongly be told that they are overweight or obese and needs to change his or her body. I think this is probably the last think we want to do to adolescents and children who already are overly concerned with how they look.

Do you guys think the BMI should be used in a situation like this? I think if the school really wanted to positively enforce a healthy lifestyle they would do so through lunch offerings, P/E classes, and by monitoring more accurate measures of one's health. It seems to me the school wants to say they support healthy living while avoiding putting more money into the cafeteria and P/E.
When I took Kinesiology we learned abit about BMI. It is useful for your average sedentary person. Any person who takes part in atheletics or even is just gifted genetically with high muscle mass it will be skewed. It originally was not meant to be used for individuals although as I mentioned before it CAN be useful for the AVERAGE sedentary person.

Doctors do use it to measure your growth as a child comparative to other children but that's a different BMI. The one you are using is for Adults only. When you get a physical by your doctor you can see them mark down the points on a chart.

Anyways you can ask your doctor or go to a gym to measure your body fat percentage. Some methods are more accurate than others obviously but I would say that none are way off. Most just mess up if you have to low a body fat percentage. For me my body fat percentage was 11.6%. Since I used to play baseball and run alot.
 
  • #11
At the peak of fitness, running 5 miles per day and lifting weights, my BMI never dropped below 25.5 - about 30 now.
 
  • #12
It is widely known that many professional athletes are considered "obese" by the BMI. As others have said, it is really only useful as a population statistic, and perhaps as a "evidence-based" starting point for discussion between a doctor and patient.

- Warren
 
  • #13
Given the limitations of what a school nurse can likely evaluate, using BMI is probably better than saying, "we looked at your kid and think he's fat" as a starting point for educating parents about their child's health and nutrition. As long as the letters sent explain that it is not foolproof, but rather worth considering a conversation with one's personal physician, it's probably better than any other measure they could have used. You don't get too many body builders in high school, and even the athletes still tend to be lanky at that age, so other than a few kids on the football or wrestling teams, it's probably going to do a decent job of identifying at-risk kids in that age group.
 
  • #14
Is there another more discerning indicator of obesity that relies only on basic measurements (not requiring special equipment) such as the BMI?
 
  • #15
junglebeast said:
Is there another more discerning indicator of obesity that relies only on basic measurements (not requiring special equipment) such as the BMI?

you could measure skin folds with calipers and run it through the equation to get %BF. you need somebody with experience doing it though, and maybe keep that job to the nurse.

still not sure how well it'd work with kids, i think all the equations I've seen were for adults. also, they all need to go through a bit of a chubby phase near puberty to spur its onset. somewhere around 11 or so, i was eating a pack of crackers a day after school and put on some chub. after going full hormonal, i was skeletor again. stuff like this has to be well thought out. you don't really want them fat in elementary school because it will help spur early onset of puberty. and then you probably don't want to keep them skinny forever to delay it.
 
  • #16
Proton Soup said:
you could measure skin folds with calipers and run it through the equation to get %BF. you need somebody with experience doing it though, and maybe keep that job to the nurse.
And I'm not really sure how accurate that method is either.

still not sure how well it'd work with kids, i think all the equations I've seen were for adults. also, they all need to go through a bit of a chubby phase near puberty to spur its onset. somewhere around 11 or so, i was eating a pack of crackers a day after school and put on some chub. after going full hormonal, i was skeletor again. stuff like this has to be well thought out. you don't really want them fat in elementary school because it will help spur early onset of puberty. and then you probably don't want to keep them skinny forever to delay it.

Yes, boys tend to get a little chubby just before that first big pubertal growth spurt. However, even so, that little chubbiness is still not even as overweight as a lot of the kids I see walking around every day who are not peri-pubertal (or at least shouldn't or wouldn't be if they weren't so overweight).

Again, it highlights the importance of parents being informed to consult a physician. Any kind of health screening in school is just that, a screening. It's not much different than using the vision and hearing tests they use in schools, which may indicate a problem, but may not indicate a vision problem (i.e., a dyslexic child might also have trouble reading an eye chart in the right order), or it might indicate the child is just having a bad day following instructions. With all of them, it's better to include more false positives than false negatives and then have a professional make the final determination. Basically, it's some way to open up a dialogue with the parents about their children's health.

Of course, I would hope it would all go along with teaching healthy habits at school too...serve nutritionally balanced, proper serving-size lunches at school, teach children what serving sizes look like, and reinstate phys. ed. classes if they have been eliminated.
 
  • #17
Moonbear said:
And I'm not really sure how accurate that method is either.

CDC sounds like they're OK with it

http://www.cdc.gov/healthyweight/assessing/bmi/childrens_BMI/about_childrens_BMI.html
How can I tell if my child is overweight or obese?

CDC and the American Academy of Pediatrics (AAP) recommend the use of Body Mass Index (BMI) to screen for overweight and obesity in children and teens aged 2 through 19 years. Although BMI is used to screen for overweight and obesity in children and teens, BMI is not a diagnostic tool.

For example, a child who is relatively heavy may have a high BMI for his or her age. To determine whether the child has excess fat, further assessment would be needed. Further assessment might include skinfold thickness measurements. To determine a counseling strategy, assessments of diet, health, and physical activity are needed.
 
  • #18
Proton Soup said:

Academy of Pediatrics. Children are completely different than adults in all terms.

The skin-fold method is slightly accurate but I wouldn't use it as an adult unless BF% is <5%. During my kinesiology regiment I set up for myself we just used hand-held devices that shoot electrical impulses through your body and measure how fast it comes back. These can be very accurate depending on the quality of the device. If you want to know without a doubt in your mind you can always do the submerging in water where they make you exhale ALL your air and take measurements that way. Or you can use something call DEXA where they take X-Ray images and measure that way. The last 2 methods are extremely expensive to have the equipment so normally only universities have them. However I'm sure you can call up a local university and ask if they do fitness testing and go in.
 
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  • #20
chroot said:
It is widely known that many professional athletes are considered "obese" by the BMI. As others have said, it is really only useful as a population statistic, and perhaps as a "evidence-based" starting point for discussion between a doctor and patient.

- Warren

That's correct muscle weighs more than fat per cubic inch, or I forgot how they compare the too.

I've heard that bringing in waist measurement into the formula helps. I've heard that underwater weighing is more effective. Then if you're really serious, opening you up after you die is the most effective :rolleyes:
 
  • #21
Sorry! said:
Academy of Pediatrics. Children are completely different than adults in all terms.

The skin-fold method is slightly accurate but I wouldn't use it as an adult unless BF% is <5%. During my kinesiology regiment I set up for myself we just used hand-held devices that shoot electrical impulses through your body and measure how fast it comes back. These can be very accurate depending on the quality of the device. If you want to know without a doubt in your mind you can always do the submerging in water where they make you exhale ALL your air and take measurements that way. Or you can use something call DEXA where they take X-Ray images and measure that way. The last 2 methods are extremely expensive to have the equipment so normally only universities have them. However I'm sure you can call up a local university and ask if they do fitness testing and go in.

I've heard that different people may store body fat differently in various parts of the body, due to heredity. So I probably should track down the source, but apparently whatever it was said some people may not get accurate readings with the calipers. However, the source did say it's quite consistent, in letting you know if your fat goes up or down, although not necessarily completely accurate. I heard that consistency of reading is important if you're trying to change body fat percentage, even if an instrument isn't accurate. So I heard that the caliper readings can vary if done by different people, but if done by the same person in the same way, it can be consistent.

I also heard that sending those electric currents through your body can be thrown off if you're more or less hydrated. Basically, I heard they rely on the principle that muscle has a higher percentage of water while fat doesn't, and measures how easily the current runs through the body. I just heard that hydration and some other factors may confound.
 
  • #22
Measuring skin fold fat tells you nothing about the amount of fat that you may have around your internal organs.

Does anyone know what the accuracy of the home weight-scales is that measure your resistance through an electric current? I was thinking about buying a new scale and was considering such a fancy one, but then it occurred to me that it probably only measures the fat content in your legs (where the current runs)?
 
  • #23
27Thousand said:
That's correct muscle weighs more than fat per cubic inch, or I forgot how they compare the too.

I've heard that bringing in waist measurement into the formula helps. I've heard that underwater weighing is more effective. Then if you're really serious, opening you up after you die is the most effective :rolleyes:

Actually, they use a water displacement tank to measure fat percentage.
 
  • #24
WhoWee said:
Actually, they use a water displacement tank to measure fat percentage.

I found it interesting because water displacement is not the only method. They can also use weighing underwater. It's used to find body density, after the air is blown from the lungs (and accounted for any left over air). From there, they use it to calculate a body fat percentage:

http://www.mb-soft.com/public2/bodyfat.html For a discussion if you want to create your own weights and floats. Water displacement is not the only method.
 
  • #25
Monique said:
Measuring skin fold fat tells you nothing about the amount of fat that you may have around your internal organs.

Does anyone know what the accuracy of the home weight-scales is that measure your resistance through an electric current? I was thinking about buying a new scale and was considering such a fancy one, but then it occurred to me that it probably only measures the fat content in your legs (where the current runs)?

Although Wikipedia is less credible, this is what I found there:

http://en.wikipedia.org/wiki/Body_fat_percentage#Measurement_techniques

Something that makes me worry about the bioelectrical impedance analysis is when I look at the ratings of those weight-scales at Amazon.com, many customers give complaints that it will drastically change in its results, just by taking a shower or eating. I've used the handhold ones owned by others and they do seem to vary back and forth. Of course more professional ones are probably better. http://en.wikipedia.org/wiki/Bioelectrical_impedance_analysis points out that they used to be not so good, but are getting better over time, but still not gold standard.

Personally, I'd prefer the calipers because although they only measure skin fat and not organ fat, they do appear to be more consistent. Although they can't be accurate, if they're done the same way some like it how they can reliably tell you if body fat goes up or down over time, which is what you want if you have a goal of either losing or gaining fat. They just have to be used the same way and by the same person.
 
  • #26
27Thousand said:
Personally, I'd prefer the calipers because although they only measure skin fat and not organ fat, they do appear to be more consistent. Although they can't be accurate, if they're done the same way some like it how they can reliably tell you if body fat goes up or down over time, which is what you want if you have a goal of either losing or gaining fat. They just have to be used the same way and by the same person.
But the area where people store fat is highly variable, how many places would you need to measure to get an accurate reading?
 
  • #27
Monique said:
But the area where people store fat is highly variable, how many places would you need to measure to get an accurate reading?

It's normally about 3-7 different places. The technique is quite accurate though just not the BEST way. It is quick though. As well if your just measuring body fat LOST then it doesn't matter about the accuracy as long as the general trend is downward.

Hydration does effect the electircal impulse as does eating specific types of food etc. Your not supposed to do these things before taking measurements to ensure greatest accuracy... but its the same as the skin method as long as the general trend is down it doesn't matter. People who need accurate measurements are people into bodybuilding competitions or taking for photoshoots. As well many atheletes have their body fat monitored but I doubt its very often.

The atheletes will do tihs at the beginning of their career to set specific goals and determine what they need to work on. But the fitness tests they do are MUCH more intense than anything me or you would even want to consider attempting in fact sometimes it's even dangerous.
 
  • #28
Monique said:
But the area where people store fat is highly variable, how many places would you need to measure to get an accurate reading?

You're absolutely correct! I'm only saying I would use calipers more than the electric current measurements, since the current is affected just by eating or taking a shower. Of course anyone can be wrong, but that's the knowledge that I have so far. Someday, maybe I'll get professionally tested. This is something that influences my thinking about the calipers:

"The accuracy of these estimates is more dependent on a person's unique body fat distribution than on the number of sites measured. As well, it is of utmost importance to test in a precise location with a fixed pressure. Although it may not give an accurate reading of real body fat percentage, it is a reliable measure of body composition change over a period of time, provided the test is carried out by the same person with the same technique."
http://en.wikipedia.org/wiki/Body_fat_percentage#Skinfold_methods

So calipers are not accurate in knowing body fat, but rather figuring out if it goes up or down over time, if you're trying to work on that. The scales make me less confident.

This is something I used when measuring: http://www.linear-software.com/online.html

They have a section for men, and one for women, using the Jackson/Pollock 7 Caliper Method, Parrillo Caliper Method, etc.
 
  • #29
Monique said:
But the area where people store fat is highly variable, how many places would you need to measure to get an accurate reading?

My kids have told me on several occasions how impressed they are with the efficiency of my fat storing system.:rolleyes:
 
  • #30
Sorry! said:
Academy of Pediatrics. Children are completely different than adults in all terms.

The skin-fold method is slightly accurate but I wouldn't use it as an adult unless BF% is <5%. During my kinesiology regiment I set up for myself we just used hand-held devices that shoot electrical impulses through your body and measure how fast it comes back. These can be very accurate depending on the quality of the device. If you want to know without a doubt in your mind you can always do the submerging in water where they make you exhale ALL your air and take measurements that way. Or you can use something call DEXA where they take X-Ray images and measure that way. The last 2 methods are extremely expensive to have the equipment so normally only universities have them. However I'm sure you can call up a local university and ask if they do fitness testing and go in.

don't be silly. rarely does anyone get down to 5% bodyfat unless they're a bodybuilder getting ready for a show or a photoshoot. calipers work just fine unless you're really obese, and then you don't need them to know you're fat.

yes, DEXA is highly regarded.
 
  • #31
Monique said:
Measuring skin fold fat tells you nothing about the amount of fat that you may have around your internal organs.

Does anyone know what the accuracy of the home weight-scales is that measure your resistance through an electric current? I was thinking about buying a new scale and was considering such a fancy one, but then it occurred to me that it probably only measures the fat content in your legs (where the current runs)?

yes, skin folds don't tell much about visceral fat. but luckily, if you're a woman, you probably don't have much. and if you're a man, you may store visceral fat more easily, but it's also the first and easiest fat to get rid of.

those bioimpedance scales don't work very well at all. but if you use them at the same time of day (say first thing in the morning), you should be able to track a trend OK, even if the actual number isn't all that accurate.

Monique said:
But the area where people store fat is highly variable, how many places would you need to measure to get an accurate reading?

at least three for males. there are different equations for male and female. for example, men tend to store more sub-q fat on the abdomen, while women store more of it on the hips.
 

1. What is BMI and how is it calculated?

BMI stands for Body Mass Index, and it is a measure of body fat based on a person's height and weight. It is calculated by dividing a person's weight (in kilograms) by their height (in meters squared). The resulting number is then used to determine if a person falls into the underweight, normal, overweight, or obese category.

2. Can BMI accurately determine if someone is obese?

While BMI is a widely used measure of body fat, it is not always accurate. It does not take into account factors such as muscle mass, bone density, or body composition. This means that someone with a high BMI may actually have a healthy amount of body fat, while someone with a low BMI may have too much body fat.

3. What other factors should be considered when determining if someone is obese?

Aside from BMI, other factors that should be considered when determining obesity include waist circumference, body fat percentage, and overall health and lifestyle habits. These factors can provide a more comprehensive understanding of a person's body composition and overall health.

4. Can a person be considered obese even if their BMI is within the normal range?

Yes, it is possible for a person to have a normal BMI but still have a high percentage of body fat. This is known as "normal weight obesity" and can increase the risk of health issues such as heart disease and diabetes. It is important to consider other factors besides BMI when assessing a person's overall health.

5. Is it possible for someone with a high BMI to be healthy?

Yes, it is possible for someone with a high BMI to be healthy. BMI is just one measure of health and does not take into account factors such as muscle mass and overall lifestyle habits. It is important to focus on overall health and not just a single number on the scale.

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