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16 November 2010

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LeeAnn Balbirona

I get light-headed long before my stomach ever growls. A sure sign I need some protein to keep me going.

Today I had two cups of coffee for "breakfast" and then got light-headed around noon. I ended up with one of those Starbuck's fruit, nut & cheese trays for lunch --minus the sesame wheat crackers since I'm gluten intolerant (how hard would it be to put rice crackers in there?!). Good for another few hours.

MelanieB

For me irritability and anxiety usually show up long before I feel hungry or my stomach growls. When I start snapping at the kids, it usually a sure sign that I need to stop and eat. Funny because when they get whiny and fussy it usually means they need to eat too. So if I lose track of time it usually turns ugly as the kids start fighting with each other and I start yelling and then it hits me that it's snack time or lunch time.

MelanieB

And now I just remembered the comment I meant to leave earlier....

I was just wondering about BMI today and realizing that I have no idea how those ranges were established. Bearing, do you know what studies were done, what criteria were used to determine what is a healthy range for BMI?

bearing

It's "convenient but inaccurate." Which means that I find it moderately useful. (Remember that my background is in engineering!) (yes, this is meant to be a self-deprecating joke of sorts)

It works better for middling-height people than for short people or tall people, and better if you're not very, very lean, to answer the subjective question "Should I lose weight?"

Body fat percentage is probably a better measure to go by. It's much harder to MEASURE accurately, though, and I can't measure it over the internet at all. (And in the case of my reader who wrote this email, the first thing I wanted to do was clear up the idea that the amount of body fat she has is the amount of weight she has to lose. But from other information she sent me, I suspect her body fat percentage was underestimated.)

Another thing about the BMI, if researcher/author Walter Willett (_Eat, Drink, and Be Healthy_ ) is to believed, is that the BMI cutoff between "normal" and "overweight" should have been revised downward to -- I think I remember it was 22 or something? Because at BMI~22 was where the death rates started to rise with increasing BMI.

An even easier-to-calculate number that correlates with a lot of health markers is simply waist circumference. However, I don't know how to turn "I need to decrease my weight circumference by 4 inches" into "I need to lose about xxx pounds, so I need to drop about xxx calories per week..."

At any rate, BMI strikes me as a decent (because easy to calculate) FIRST approximation for obese people to use to decide about how much weight they should try to lose. It does not give you an accurate number; it gives you a first target. Once you get near there, you can look around and see if it's about what you want to be.

Which is kind of how I used it. I have had a BMI as high as 32.3. When I started to lose weight, I decided I would stop when I got below 22 (picked that number from Walter Willett's book mentioned above). I lived at 21.8 for about six months and decided I felt too thin; after my next pregnancy, I deliberately brought my weight only down to a BMI of about 23. That seems to be a pretty good weight for me -- I feel very comfortable and I don't look gaunt.

So, I found it very useful just for taking a stab at a "goal weight." Mind you, I understood from the beginning that it was only a first approximation of what would be "healthy" for me.

bearing

Oh, and as to where it came from, what studies, etc. It's properly a tool for studying populations, not individuals, and as a "simple means of classifying" people (which is really how I used it to decide on my first-guess goal weight).

"While the formula previously called the Quetelet Index for BMI dates to the 19th century, the new term "body mass index" for the ratio and its popularity date to a paper published in the July edition of 1972 in the Journal of Chronic Diseases by Ancel Keys, which found the BMI to be the best proxy for body fat percentage among ratios of weight and height;the interest in measuring body fat being due to obesity becoming a discernible issue in prosperous Western societies.

"BMI was explicitly cited by Keys as being appropriate for population studies, and inappropriate for individual diagnosis.

"Nevertheless, due to its simplicity, it came to be widely used for individual diagnosis, despite its inappropriateness.

BMI provided a simple numeric measure of a person's "fatness" or "thinness", allowing health professionals to discuss over- and under-weight problems more objectively with their patients."

(And an easy way for anyone to write about weight on the internet, I add.)

"However, BMI has become controversial because many people, including physicians, have come to rely on its apparent numerical authority for medical diagnosis, but that was never the BMI's purpose; it is meant to be used as a simple means of classifying sedentary (physically inactive) individuals with an average body composition."

(which is how I use it when I write about it -- I should probably start using a disclaimer)

"For these individuals, the current value settings are as follows: a BMI of 18.5 to 25 may indicate optimal weight;"

(except that some people point out that really "optimal" should only go up to 22)

"a BMI lower than 18.5 suggests the person is underweight while a number above 25 may indicate the person is overweight; a BMI below 17.5 may indicate the person has anorexia nervosa or a related disorder; a number above 30 suggests the person is obese (Al C) (over 40, morbidly obese)."

Or to put it more succinctly, if someone writes me and says "I'm 5 foot 7 and 217 pounds," the BMI lets me do a quick calculation and say "oh, I see, yes, you are probably obese." Otherwise I would be like, "um, 217 pounds... I guess that sounds like a lot, but you're five foot seven..." I've got lots of experience with and intuitive grasp of the varying weights/obesities that a 4-foot-11 person can be, but none with 5-7 people!

bearing

(sorry, all that quoted material is just from wikipedia.)

MelanieB

Thanks, bearing, that is all really helpful. I suppose I could have gone to wikipedia myself, I do it all the time; but somehow that didn't occur to me for this question.

Having always had a quick metabolism and a tall, skinny frame, weight was never an issue that doctors brought up with me until I started having babies. Then I gained 40 pounds with my first pregnancy and the doctor cautioned me about my weight gain.

Though I always sort of knew my eating habits weren't all that healthy and I even used to joke that at some point bad dietary habits and a sedentary lifestyle would catch up with me. So my first experience of even looking at my BMI was in terms of postpartum weight. I think it was about 25 after Bella was born, 27 after Sophie. Right before this current pregnancy I'd got it to where I was within a pound or two of 24. So definitely above the optimal of 22 but definitely never near obese.

Not being a person who has ever struggled with obesity, I've wondered how concerned I really need to be about carrying a bit more weight as long as I'm still nursing a baby. I've always wondered how applicable it is to use BMI when you are in a situation like mine where for the past five years I've been pregnant then nursing then pregnant again before the previous baby weaned. Is 25 still above optimal for postpartum nursing moms? Is there any specific data for that population and would it be different than the population at large?

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