BMI's and accuracy.

[Beth]

I was looking at a past issue of Nat Geo that dealt with us fat Merkins. Yes, it was sadly true that we gorge ourselves on food and are probably much more gluttonous than we were thirty years ago, although I cannot recollect that time.

Anyhoo, I looked once again at a BMI chart. I realize that 19-24 is a healthy weight, 25-29 is overweight, 30-34 is obese, and 35+ is moderately to morbidly obese. Okay. Here is the thing. I know my weight and BMI since I am weight obsessed and cannot seem to lose one freaking pound but I asked hubby about his weight once again because I was stunned what the chart said. According to his weight and height (6'2" and 225lbs), his BMI is right around 29. Now, this has my dear hubby in the overweight category and nearly at the obese mark. Hubby is trim, muscular and only has a wee wittle pudge on his tummy. He is large, but the bulk is most definitely muchly caused by muscle.

I, on the other hand, have a BMI of 22. I am in the normal weight category, but I consider myself downright chunky. I do not have the muscles hubby does, although I am very strong for a poor female;).

Now, the BMI has hubby in a danger category, though trim and not too much fat on his body, but me in the healthy category although I do have tons more fat on my body and this just seems so very off and makes me really question how valid the whole Body Mass Index scale is.

Should we really use this scale to determine who is and is not overweight and to determine obesity? because if Americans like hubby, are being used to determine who is and is not obese (if he works out and bulks up another five pounds, he is considered obese) then I really cannot see that the claim that we are so freaking fat is really that accurate.

[Dingfod]

Most BMI calculations are near meaningless. When I was 20 years old and weighed 190 pounds, an online BMI calculator shows a 25, and I didn't have an ounce of excess fat, I was lean and strong. I couldn't "pinch an inch", to use the old Special-K cereal ad line.

About 10 years ago, I had a body fat analysis done at BYU Med Center in Provo, Utah as part of a study they were conducting. They used several methods including weighing me submersed in water and electrical resistance tests. They came up with some numbers that astounded me at the time. At 262 pounds, I knew I was overweight without a doubt. I was at that time in very good physical condition, strong and didn't get winded easily. I rode my mountain bike regularly, hiked in the mountains frequently, iceskated year round at indoor and outdoor rinks, skiied on alpine and nordic regularly during the winter and was a regular at a fitness center. BYU's testing showed I had 216 pounds of lean body mass, which even at 0% bodyfat would had me at a BMI of 28.5, over the recommended BMI. Their tests showed me at 21% body fat, needing to lose just 14 pounds to get down to the recommended 15% body fat. Of course, I questioned the numbers asking why my lean body mass was more than I weighed total when I was thin. They said it was because of my football player musculature required for making my body weight do what I was doing. Granted, you don't do 10 reps of 750 pound leg lifts without some muscle.

A few years later when I broke my ankle then followed that by cervical spine surgery and put on 30 more pounds in a half year I wasn't in quite as good a shape. Then I lost 40 pounds on Atkins. According to feedback I got from people I looked pretty good at little over 250 pounds, which calculates on the online BMI to be about 33, which they say is not just overweight but obese. I'd buy that for before I lost the weight and now that I'm back up near my peak weight, but not for how I looked and felt at the time.

Anyway, what I'm getting at is that most of those BMI calculators are far too simplistic to give an accurate number that would apply to everyone. People are all different sizes and shapes, even if they aren't overweight.

[ceptimus]

Are there different BMI calculations for males and females? If not, why not?

Who decided that the ranges of BMIs are correct and why?

We were always taught (correctly) in math that the volume and therefore mass of an object is proportional to the cube of its linear dimensions. Why is it a power of 2, not 3 in the BMI calculation? Even if you argue that taller people tend to be, and should be thinner than shorter ones, it doesn't explain the power of 2. Maybe it should be 2.4 or 2.7 or something.

[Dingfod]

Other examples of exceptions to the BMI guidelines, two guys that share my frame size, my dad and my brother Jim. Both are 6'1" and they both weigh about 210-215 pounds, which is overweight according to the BMI calculations. I don't know about Jim, but on my dad you can see his ribs and only has the slightest roll at his waist, not bad for a man of 71.

My other brother is a freak, 6'4" and somewhere around that same weight, the freak.

[LadyShea]

BMI is only one indicator and it does not take muscle, gender or frame into account at all. Mine is within normal, but I am very small framed and am overweight for myself at this point. I have a friend who is the same height as me, but her frame is so much larger...her shoulders are a full 4 inches wider than mine....no way we should weight the same or even close to the same.

Use BMI in conjunction with other things like body fat tests and your own good sense.

[seebs]

I gave up on BMI. I'm a little pudgy, but BMI says I'm morbidly obese. I think it presumes that you take no exercise whatsoever and have barely muscles enough to move your limbs.

[Adora]

BMI doesn't account for muscle weight, differences in bone density, or general wellbeing and fitness (which you can have quite easily even if you are in the upper reaches of the BMI range).

So no, I don't use them anymore because of this. I know my healthy weight range, but I also know when I am feeling fit and healthy and when I'm not.

[Dingfod]

I gave up on BMI. I'm a little pudgy, but BMI says I'm morbidly obese. I think it presumes that you take no exercise whatsoever and have barely muscles enough to move your limbs.Which is me right now. Jabba the Hut, move over you skinny bastard.