Thursday, November 13, 2008

Ban the BMI?

You know the BMI (Body Mass Index), right? It's a number that represents a relationship between your height and your weight, and is supposed to be a decent predictor of chronic disease risk (go HERE to calculate your BMI).

Well, step aside, BMI: According to a new study, a simple measurement of waist size is an even better predictor. The study, published in the New England Journal of Medicine, found that a large waistline increases the risk of premature death even for people who are not technically overweight. In fact, the heaviest 20% have twice the risk of dying, according to the research.

The authors conclude, "These data suggest that both general adiposity andabdominal adiposity are associated with the risk of death and support the use of waist circumference or waist-to-hip ratio, in addition to BMI in assessing the risk of death," meaning, in English, that waist circumference and/or waist-hip ratio will give us more information than just the BMI -- but not to scrap the BMI, just use both measurements to better assess risk of death.

There are strengths and weaknesses to all methods of body measurement in predictability of death: for one, skeletal sizes vary, so what is slender to a large-framed person might be overweight for a small-framed person. Second (this is the main weakness of the BMI), having a lot of muscle mass will put a potentially very fit individual into the "obese" BMI category. Third, for waist circumference and waist-to-hip ratio, there is inherent measurement error (give three people a tape measure and a subject, and you're likely to get 3 different measurements, because there is variation in angle of the tape measure, the placement of the tape measure, and the force with which the tape measure is pulled around). Regardless, these measurements are still useful- as part of a larger assessment that includes diet, exercise, and genetics- to predict death and disease risk. Of course, what many people forget is that ALL of us have some degree of risk, and of course our overall risk of dying is, indeed, 100%. What we care about is, not dying because we're not healthy (as opposed to dying of simple old age).

If this sounds too clinical for you, then let's get back on the ground and look at the big picture: Eat right (and not too much) and exercise, and these measurements won't mean much for you. Maintain a healthy body with lean muscle and minimal fat, and you can be sure that your chances of living long and healthy will skyrocket.

But it's not all about weight. I could get skinny on a diet of tea and celery, or I could be far healthier with a little more "meat" on me and optimally nourished. That's why vegan nutrition is so exciting to me. We, as intelligent, free people in charge of our bodies and with real control over our fates, have the power to feed our bodies the healthiest foods and to move our bodies in the healthiest ways. What a privilege! We have this incredible gift: a body, that is all ours, the only thing, really, that belongs to each of us 100%. We have the power to choose when to say no, when to push ourselves away from the table, when to take seconds, and when to exercise. We have the power to choose the foods we put into our bodies and how much, to lift heavy objects or jump up and down or walk rather than drive. Yet so many of us take this freedom for granted, and become slaves to our jobs and other responsibilities. Not that these things aren't important: they're just not MORE important than keeping ourselves healthy. So make your good health a priority today. You and your loved ones will thank you.

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