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Tuesday, September 17, 2013
Dear Dr. Camardi:
As a retired certified diet and nutritionist, I found it fascinating how you discussed the Body Mass Index recently as it pertained to my parents.
You turned everything that I thought was true and had learned for years about the BMI upside down in less than 5 minutes.
When you told them they could have the scoop of ice cream, peanut butter, some chocolate and other things in moderation that I took away from them, if they did more walking and stretching I thought they were going to have a party right then and there!
I think I understood what you said about the “obesity-mortality” paradox but could you spell that out again?
Before we begin, nothing of what we will be talking about is an excuse to revert back to being a couch-potato and breaking out the chips and beer. And to those who are thinking, “They tell us to do all these things and then give it a few years and they’ll tell us to do the opposite”— I hear you.
What we are going to talk about is only a measuring tool that we have found to be less than perfect, especially when it comes to seniors. The issue is that the BMI has been inappropriately used by many as a means of judgment instead of a single tool in evaluation.
To begin with, the BMI is the result of a calculation using your height and current weight — and right there is problem number one.
Height and weight are only two of other variables to measure fat. To continue, divide your weight in pounds by the square of your height (problem number two, see below) in inches multiplied by 703.
The acceptable range of BMI is 18.5 to 24.9. A BMI under 18.5 is considered underweight, while a BMI between 25 and 29.9 is considered overweight. BMIs over 30 are labeled obese.
For seniors, controlling weight through prudent exercise and diet is still the goal. It’s just that the goalposts have been moved a little bit!
My journey with BMI began almost 10 years ago in New York when I was privileged to take care of a number of retired sports figures.
They came in all shapes and sizes and when we did their intake measurements and vital signs, many of their BMIs were in the “obese” range, yet I can tell you that as we would train for 5K runs, they were in shape.
At that time BMI was the rule but I had my doubts. Well, other physicians did also and I added BMI to my study list of topics that I would follow.
In a relatively short period of time, it became clear that BMI had some real issues. The Centers for Disease Control feels that BMI is a dependable presentation of a patient’s body fat when compared to other more cumbersome means. However the CDC feels it should not be used to diagnose obesity.
We do not have a reliable means to economically diagnose obesity. It was this little caveat that tripped up a lot of people .
And then something else happened on our way to the celery and carrots: Geriatric patients with high BMIs lived longer and withstood the ravages of serious diseases better than patients with lower BMIs.
This is the “obesity-mortality” paradox. I think the body calls upon the extra stored energy in time of disease and uses it to help us recover. How much we should store so that it does not become a cardiovascular disease risk needs to be determined.
It turns out that the overweight designation, or a BMI between 25 and 29.9, is an indicator of cardiovascular mortality risk in younger adults, but some feel that 27 instead of 25 should be the limit of BMI in geriatrics.
We knew that as you age, you lose muscle mass. This natural process is called sarcopenia, and as muscle mass decreases, fat tissue centralizes around your trunk and waist, filling in the bulk area where muscle was. You also tend to store more fat as age progresses, thus maintaining steady or slightly increasing weight.
So, treating seniors with a BMI in the mildly overweight range as if they were younger adults may cause more harm than good.
What I feel is a more reliable index, but still of questionable value, is waist size.
Studies show that cardiovascular risk goes up with a waist size that is more than 35 inches for women or more than 40 inches for men.
The key for me is geriatric fitness that improves aerobic capacity, maintains tolerable muscle mass and provides for flexibility and balance.
As we age we have to approach this challenge gently so as not to cause more problems. This brings to mind the question of whether one can be “fit and fat.”
Depending upon which tool one uses, the answer is yes. How much fat is tolerable to limit cardiovascular and cancer risk? Nobody really knows the answer to that question and frankly the likelihood is that we may never know.
The key here is to sit down with your doctor and decide what makes sense — until we in the profession come up with the “next big thing.”
Dr. Michael Camardi is a geriatrician at the Carilion Center for Healthy Aging and an assistant professor of medicine of the Virginia Tech Carilion School of Medicine. His column runs monthly in Extra.
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