Medicine For People!
Size, Shape, and Longevity
- Met Life Tables
- Body Mass Index
- White Fat vs Brown Fat
- ABSI: A Body Shape Index
- What's in a Number?
- Met Life Tries Again
- It's Just a Number!
Met Life Tables
In 1943, the Metropolitan Life Insurance company published one of the first measures of health and longevity, tables of ideal weight for people of various heights. While these tables have been revised over the years, many doctors believe these tables set unrealistic standards of health.
Initially, we used these tables to evaluate the effect of weight on longevity. Now we realize that extra weight on an older person can be a benefit, not a handicap. An older person, for example, is more likely to fall ill and be unable to eat for a period of time. Who is better off, the man with extra fat onboard to fuel the healing process, or the one without?
Body Mass Index
More recently, the body mass index (BMI) has become popular as a measure of health. If you want to know your own BMI, the National Institutes of Health has an online calculator you can use. However, the formula used to calculate the BMI is inaccurate for people who are tall or have a large frame. Both Arnold Schwarzenegger and Sylvester Stallone had, in their prime, a BMI of 33 or higher. A BMI over 30 is supposed to indicate obesity. Whoops! In fact, the BMI was never intended for individual use. It is a statistical tool for population researchers.
White Fat vs Brown Fat
Everyone recognizes that the ratio of muscle to body fat impacts health, but so does the type of fat we have. White fat—which accounts for almost all body fat—is a mixed blessing. On the one hand, it can cause aches and pains, blood clots, and man breasts, but on the other it contributes to a youthful skin and can save your life during serious illness. Brown fat, which is found in greater amounts in lean people, is in general desirable, keeping us warm in cold weather, burning energy, and keeping weight down. This is just one of several reasons the BMI can mislead us.
ABSI: A Body Shape Index
While several replacements for the BMI have been proposed, ABSI (A Body Shape Index) seems to be leading the pack as of now.
ABSI produces a better prediction of health and mortality than BMI at little expense, requiring just a few simple measurements. Get your height, weight, and waist circumference and plug them in. That number provides a more accurate prediction of mortality than BMI or the Met Life tables can provide.
What's in a Number?
The only reason to do these calculations is to guide your behavior. When we're 20 years old, the end of life is impossibly far away. Snickers bar? BMI? Who cares? But as the end of life comes nearer, or health measures such as blood pressure and blood sugar rise, I've seen many people engage in real behavior change, resulting in measurable health improvement.
And so, an ABSI showing a doubled risk of death can be useful. The person looking at that number can realize that losing an hour a day to their exercise program is much preferable to spending 24 hours per day under a tombstone.
Met Life Tries Again
The ABSI, while based on careful research, gives your risk compared to an average and looks only at body shape.
Met Life offers this more up to date tool that estimates how many years you have left. As a life insurance company, they have physical exam reports on millions of people. Sooner or later they do find out how long each individual lives with their particular physical measurements. Met Life's newest effort, as you can see, takes more into account than just body size or shape.
It's Just a Number!
Look at the people around you. Do you see anyone who looks anything like you? Probably not! For all our great differences in appearance, the differences in individual physiology, metabolism, and internal chemistry are far greater. That's why the medicine that works so well for you does nothing for your neighbor. And so the ABSI and both efforts from Met Life are still just numbers.
The BMI is useful only for those who wish to feel guilty. You can be healthy with any shape. Don't let a number get in the way of vigorous activity or healthy nutrition or your enjoyment of life. And remember what Mark Twain wrote--- "Be careful about reading health books. You may die of a misprint!"
Edited by Jody Bowers
Medicine for People! is published by Douwe Rienstra, MD at Port Townsend, Washington.