What's the deal with BMI?

[Arch]

Saw a doc a few days ago, and he later mailed me a printout with my height, weight, and BMI estimate, plus an insert with BMI ranges. He seems to want me to lose another eight or ten pounds. I've actually been working on it for a couple of months for my own reasons--basically looks, not health--but I am not making much progress lately. More weight loss will take a GREAT deal more effort--or liposuction.

I'm actually a little taller than he thinks, but not by much. And my clothing weighed about five pounds that day. But even with the added height and stark naked, I would still come up as borderline overweight by the BMI estimate. I find this irritating.

I did a little reading online but don't really have the time or the inclination to get into it much. If you're in the health field and actually know something about this, how the heck do doctors justify measuring men and women equally, and how can they not take body type into account? A woman with my height and weight is likely to have less muscle and more fat than I do, and I am not lightly built...why is the same system apparently used for both sexes and all body types? Or do the broad ranges account for sex/gender and physical variance?

[supremecatoverlord]

As far as muscle goes, BMI does not account for muscle mass - so a bodybuilder who has visible abs might be considered overweight by its standards. I don't know how lean your body looks or even if muscle might account for part of your problem, but I just thought I would say.

[LivingInGrey]

Yeah, the body mass index system is flawed. As you said both men and women are measured just the same on this system which is red flag number one in my opinion. As the other poster said body builders with like 6% body fat could still be classed "morbidly obese".

Get your body to what you feel happy with so long as it's done in a healthy fashion. Anything less then 6% body fat (for a man) is unhealthy. Best way to judge what your body fat is, if you can see your ab muscles your in the 6% body fat range.

If you want to knows exactly what your % body fat is you'll have to see a personal trainer and have a calapir test done (not the most accurate but far more accurate then the bmi system).

To help drive this concept home I have a story. I have a friend of mine who is a career Marine. Once a year he has to LOSE weight though he maintains 8% body fat in order to be able to stay in the Marines. He told me that three months before his physical he has to stop lifting, reduce his protine intake and eat mostly vegetables in order to keep his % of body fat from getting to high. He said it's silly but the computer will not take into account his athletic physic into account for his "weight issue".

[Cindy]

Can I throw in a few cents worth?

What many medics are concerned about is the so called metabolic syndrome that may predict an increased risk of diabetes, heart disease, premature death or disability.

The BMI is a sort of indicator but has to be taken into perspective.

So, please bear with me.

Waist circumference is often used to assess abdominal fat content, excess abdominal fat, out of proportion to total body fat is an indicator of risk factors associated with obesity.

Undesirable waist circumference differs for men and woman. In this instance gender is defined by chromosome status, taking into account hormonal profile. So yes if you have have been on male hormones for some time then you should move into the male profile. I cannot find information on 'how long' is. The people behind the studies didn't include TG people.

Men are at risk if their waist measurement is >40 inches. Woman if >35. This is based on 'average' males and females. I am not regarded as a biologically average female, you are probably not regarded as an average male.

OK. Now the calculation takes into hip measurement. And of course this is where MtF and FtM can get into odd situations. For both genders a waist-hip ratio of 1.0 or higher is taken at risk. For men a ratio of 0.90 or less is considered safe. For woman 0.80  or less is safe.

Since your hip size probably was set during puberty it is regarded as male or female at that time. My ratio is 0.88, they are considering me at low risk as I have a male shape, even though I'm female. In your case they are using a female profile even though you are male.

BMI has a less gender specificity. a BMI of 25-30 is overweight. A BMI of 30+ is obese. These targets are set for average people. Athletes etc have unusual BMI and the factor becomes irrelevant. Somewhat analogous to blood pressure. Normal blood pressure is set on average people. Athletes etc are excluded, their BP is not normal in most cases. For example most elite professional cyclists have a resting BP that is so low that they would be taken to a ICU.

So the take home message is to get your BMI lower than 25 and to get your waist-hip ratio below 0.80. If you have a very masculine body structure use the male figures. And remember the numbers are averages based on a Gaussian distribution. We (TGs) skew that distribution so take that into account as well.

I hope that helps?

Cindy

[Jamie D]

Can I throw in a few cents worth?

What many medics are concerned about is the so called metabolic syndrome that may predict an increased risk of diabetes, heart disease, premature death or disability.

The BMI is a sort of indicator but has to be taken into perspective.

So, please bear with me.

Waist circumference is often used to assess abdominal fat content, excess abdominal fat, out of proportion to total body fat is an indicator of risk factors associated with obesity.

Undesirable waist circumference differs for men and woman. In this instance gender is defined by chromosome status, taking into account hormonal profile. So yes if you have have been on male hormones for some time then you should move into the male profile. I cannot find information on 'how long' is. The people behind the studies didn't include TG people.

Men are at risk if their waist measurement is >40 inches. Woman if >35. This is based on 'average' males and females. I am not regarded as a biologically average female, you are probably not regarded as an average male.

OK. Now the calculation takes into hip measurement. And of course this is where MtF and FtM can get into odd situations. For both genders a waist-hip ratio of 1.0 or higher is taken at risk. For men a ratio of 0.90 or less is considered safe. For woman 0.80  or less is safe.

Since your hip size probably was set during puberty it is regarded as male or female at that time. My ratio is 0.88, they are considering me at low risk as I have a male shape, even though I'm female. In your case they are using a female profile even though you are male.

BMI has a less gender specificity. a BMI of 25-30 is overweight. A BMI of 30+ is obese. These targets are set for average people. Athletes etc have unusual BMI and the factor becomes irrelevant. Somewhat analogous to blood pressure. Normal blood pressure is set on average people. Athletes etc are excluded, their BP is not normal in most cases. For example most elite professional cyclists have a resting BP that is so low that they would be taken to a ICU.

So the take home message is to get your BMI lower than 25 and to get your waist-hip ratio below 0.80. If you have a very masculine body structure use the male figures. And remember the numbers are averages based on a Gaussian distribution. We (TGs) skew that distribution so take that into account as well.

I hope that helps?

Cindy

Case in point ... ME

Early 2012
Coronary heart disease
Type II diabetes
Central obesity (pot belly)
Fatty liver
High cholesterol
High triglycerides
Hypertension
Kidney disease
BMI=34.2

Now before you think I'm a total wreck ...

Lowered weight 25 pounds in six months
Lowered A1c to 6.7 - long acting insulin
Instituted cardio rehab program
Improved diet
Cholesterol in "normal" levels (but need to be lower) - statins
Triglycerides controlled with medication - gemfibrozil and fish oil
Microalbumin levels improved
Blood pressure under control (from unmedicated 160/100 to medicated 90/60)
BMI=30.8